Document 9LqjN3bw1w9EpO7z2JBw1r0yL
488 Annals New York Academy of Sciences
per. cage, and dosed with TCDD or corn oil. The animals were kepi in temperature~iift^btaTdlty*cMTOflcd rooms*wiih Wi-hour.lighi/dark cycle. The access to animal
rooms was limited and kepi lo a minimum. TCDD solution for dosing these animals was prepared by dissolving 5 mg of the
chemical ( > 99% purity) initially into 10 ml acetone (glass distilled) and mixing this solution with 190 ml of corn oil (Nutritional Biochemicals, Cleveland, Ohio). This, stock solution, containing 25pg TCDD/ml was diluted with corn oil containing 5% acetone to provide appropriate dosing solutions. The control group was dosed with corn oil containing 5% acetone. The concentrations of all dosing solutions were . appropriate to provide 0.1 ml/IO g to mice. The animals were weighed and dosed once a week with 0.0, 0.01.0.10, 1.0, and 10 pg/kg orTCDD, for 8 weeks. In addition, one group of mice were given a single oral dose of TCDD at 10 pg/kg body weight.
Four animals were randomly selected from each group and sacrificed at 2,4. and 8 weeks after the treatment started. Similarly, the animals were killed 2,4. and 8 weeks after a single treatment with TCDD. At the lime of sacrifice, the blood was saved for serum and selected organs were collected and weighed. The liver, kidney, and thymus were placed in formalin while the spleen was saved in sterilized saline for lymphocyte cultures.
The tissues from these animals were routinely processed and stained for histopa thologic evaluation. Microscopic examination of all organs was performed in a random-blind fashion.
Splenic Lymphocyte Cultures
Immediately after their collection, the spleens were washed wiih sterilized isotonic saline solution and mashed with a pair of forceps in saline to release their cellular constituents. The cells were separated from the intact tissue by serially passing through 18, 21. and 26 gauge needles. The solution was allowed to stand in a glass tube for nearly 10 minutes to remove cell aggregates, after which it was transferred to a different tube leaving the sediment and glass adherent materials, behind. This suspension was centrifuged at 4000 rpm for 10 minutes at room temperature and the cell pellet suspended in a small volume (3--5 m!) of culture medium. An aliquot was used for counting cells in an electronic counter after lysis of erythrocytes.
Lymphocyte transformation was, determined in cultures by.a method essentiallymodified from Alhaji et al.k The ciiliure media used was RP.MI 1640 (Grand Island Biologic2ls, Grand island, N.Y.) containing! 0% beat-inactivated fetal calf serum and 100 units of penicillin and 100 pg of streptomycin per ml. The media was supplemented with 300 pg/m l of L-gluumine. The cell suspension was adjusted to provide approximately 8 X 1 0 * cclls/ml and 50 pi of this layered into each well of t micro-tissue-culiure plate (Microtest 11. Falcon 3040. Falcon Plastic. Oxnard. Ca). To each w*ell, 50 pi of additional culture media was added and 50 pi of media cither without any mitogen or containing optimized concentrations of phytohemacglutinin (PHA. I pi. reconstituted, per culture well) or pokeweed mitogen (PWM. 1 pi. per culture w-ell, both mitogens obtained from Grand Island Biologicals. Grand Island, N.Y.). The plates were incubated for 52 hours at 3.7 C in humidified 5% CO; in air atmosphere. After this incubation. 50 pi of culture media containing 0.5 pCi of JH-lhymidine (New England Nuclear, Boston, Mass.) was added to each culture well and the incubation continued for an additional 16 hours. The cells were harvested and vigorously washed with physiologic saline using a mode! M12V Cell Harvester (Brandel, Co., Rockville. Md.) and collected on Reeve Angel 954AH glass fiber discs (Whatman, Inc., Clifton. N.J.). These discs were placed directly in regular counting
as
kept in temperatureirhc iccctMo-animil
.vtng 5 mg of the ted) ind mixing this >eve;tnd, Ohio). This rn oil containing 5% roup was dosed with csir.g solutions were iehed 2nd dcsed once ceks. In addition, one /kg body weight, scrificcd zt 2,5, znd 8 Hied 2.4, 2nd 8 wceks c blood was saved for kidney, and thymus saline for lymphocyte
i sximed for histopa*2s performed in a
i;h sterilized isotonic release their cellular by serially passing ;>s*.2nd in z glass tube was transferred to a trials behind. ^Tnis imperature and the :ium. An aliquot wax throcyies. a method essentially 16-40 (Grand Island i fetal calf serum and Ttl. The media w-as sio'n W2S*adjusted to d into each well of a Mastic. Oxiizrd, Ca). 50 ^1 of media either phvxoherr.acglutinin e.n ] aul. per icals. Grand Island, cified 5Se COj in air -r.uining 0.5 >jC> of to each culture well were harvested and 2V Cell Harvester AH glass fiber discs in regular counting
'-Vt.
Sharma & Gchring: Effects of T C D D
489
vials. 10 ml of scintillation solution (Aquasol, New England Nuclear. Boston, Mass.)
--i- added and ihc7^ d i o 3ctsvii36*counicd_iflcr..shj!tl:ing .in.: a... M^gk III Scintillation,
spectrometer (Scarlc Analytics. Inc., Chicago/1)1.). The counts were converted to
disintegrations per minute (DPM) using a standard quench curve, averaged and
adjusted for 10* cells in the culture system. All cultures were run in triplicate. The
stimulation index for PHA or PWM was calculated by dividing the DPM for cultures
in the presence of respective mitogen by the DPM for cultures in which no mitogen
was present.
...
To determine the effect of TCDD directly on lymphocytes in culture, the spleens
were collected from control animals and cultured in media containing various
concentrations of TCDD (see R esults section) as described above.
Estimation o f immunoglobulins
Total immunoglobulins in sera of ani'mals were estimated by a quantitative immunoclectrophoresis (QIEF) technique modified from Bjerrum ft at? Rabbit anti-mouse Ig, globulin fraction (BioRad Laboratories, Richmond, CA), was carbamylaied and incorporated into a 1% agarose gel plate (10 cm X 10 cm X 1.5 mm). Appropriately diluted scrum samples were applied in duplicate in wells punched into gel plates containing respective antiglobulin and electrophoresis performed (300 volts for 3-4 hours or 100 volts for 16 hours) using a Model 1400 electrophoresis chamber (BioRad Laboratories. Richmond, CA). The plates were pressed, dried and stained with coomassic brilliant blue, and the heights of rockets compared to appropriate standard samples in the same plate. A pooled mice scrum sample (pooled from juvenile male animals) was used as a reference standard and all Ig concentrations represented as a ratio to this pooled sample.
Statistical Analysis
The values are represented as means and standard deviation or standard error of means. The" para meters of treatment group were compared to those in the respective control group by using a t-test. In sonic cases, two-way analysis of variance was performed. The body weights, organ weights and their ratios were compared using a* Dunnctt's V.*
R esults
TCDD produced toxicologic manifestations in mice at high levels of exposure. Their body and organ weights, at different periods during the experimentation, arc given in T a b le I. As indicated, the increase in the body weight of mice exposed to 10 tg/kg/wfc TCDD for 8 weeks was due to the accumulation of ascitic fluid (animals with severe ascites were not sampled). The only definitive changes in organ w-cighis were increased liver weights in mice receiving 10 mz TCDD/kg/week.
Histopathologic examination of organs showed consistent treatment-related changes only in mouse livers. The hepatic changes were similar to those described previously for rats/ The lesions ranged from swelling and vacuolation of hepaiocytes to autolysis and necrosis (both focal and diffuse) of parenchymal tissue. The lesions were primarily in peripheral lobular regions and in some cases nearly -6 of the total tissue indicated extensive necrosis. Some sections also exhibited fibrosis, increased
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Annals New York Aendemv of Sciences
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Qhg/.h a hi finny Weights of Mu:r T kc a rr.n w ith TCDO ron [ ) ii->i:.ri;nt Ihturvaiji
r.xpmuire llndy
Duration of
Level
V/ci|'.lt
lisptmin: /if./kg/wcek (G)
Thymus
Cg) <r./i00g)
Of gun Weights and Their Relation to ilmly Weight
Spleen
Liver-
(r.) (b/ iooc) (g)
(g/lOO)
Kidney is) (s/lOOfi)
1`icdxpnsurc ' 0
28 A 4 0.05 A 0.01 0.1K A -0.02 0.09 a 0.02 0.31 * 0.06 1.67 a 0.24 6.06 a 0.35 0.48 a 0.07 1.75 a 0.09
2 weeks <
0 o.nt 0.1
10
)J A 1
36 A 1 36 A 2 35 A 2 35 A 2
0.07 A o.m 0.20 A*0.03
0.06 A 0.01 0.17 A 0.03 0.07 A 0.01 0.1K A 0.02
0.05 A 0.01 0.13 a 0.011 0.06 A 0.01 0.16 a 0.01
0.07 *0.01 .20 a 0.04 1.90 * 0.17
O.OK ;fc 0.01 0.23 * 0.03 1.99 a 0.11
0.1(1 a 0.021 0.2H* 0.03 2.12 a 0.20 0.10 * 0.011 0.27 * 0.03 2.24 a 0.15
0.09 * 0.02 0.26 * 0.06 2.77 a 0.32J
5.79 a 0.42 5.53 A 0.32 5.87 a 0.21 6.36 a 0 J9 7.83 a 0.57J
0.55 a 0.05 1.69 a 0.03 0.56 a 0.05 1.55 a 0.15 0.35 a 0.06 1.52 A 0.15
0.64 a 0.06 1.81 a 0:10
0.37 a o.oi >.6i a <n
4 weeks
Of 0.01 0.1
'.10
38 A 3
39 a 3 39 A 3 38 A 5 37 A 2
0.06 A 0.02 0.16 a 0.04 0.04 A 0.02 0.11 a 0.05 0.04 A 0,01 .0.10 a 0.03
0.05 A 0.01 0.13 A 0.03i 0 .0 }t u 0.01 0.0K a 0.04
0.09 * 0.03
0.09 * 0.02 0.07 rf, 0.02 0.09 * 0.02
0.11 * 0.0-1
0.25 * 0.05 0.24 a 0.03 0.19 * 0.03 0.24 * 0.06 0.30 * 0.10
1.94 a 0.32 1.91 a 0.20 2.00 a 0.24 2.32 a 0.34 2.79 A 0.531
5.14 a 0.53
4.92 a 0.38 5.16 a 0.46 6.11 a 0.90 7.54 a 0.941
0.55 a 0.07 1.45 a 0J09 0.58 a 0.07 1.48 a 07l0 0.5X a 0.07 1.48*0-16 0,61 a 0.10 1.39 a 0,17 0.62 a 0.11 1.68 a 0.24
8 weeks
0 0.01 0.1
10
40 A 1 39 A 4
42 A 3 44 A 4 49 A 3!
0.05 A 0.01 0.06 A 0.02 0.07 A 0.03 0,07 A 0.01
0.05 A 0.01
0.13 A 0.01 0.16 a 0.05 0.16 a 0.07 0.16 a 0.04 0.11 a 0,02
0.09 * 0.01
0.13*0.10 0.11 * 0.0-1 0.11 * 0.02 0.11 0.03
0.23 a 0.04 1.96 a 0.19 0.34 * 0.29 2.03 a 0.16 0.26 * 0.12 2.30 a 0.17
0.25 * 0.05 2.X) a 0.22t
0.23 * 0.06 3.28 A 0.361
4.92 a 0.43 5.19 a 0.27 5.50 a 0,0K 6.49 a 0.411
6.73 A 0.46J
0.57 a 0.02 0.54 a 0.09 0.60 a 0.07 0.60 a 0.07 0.36 a 0.03
1.43 A 0.07 1,38 a 0.23 1.43 a 020 1.36 a Oil3 1.16 a Oil I
*Mean A S.f). of 4 animal* per roup, except ns indicated. {Only 3 animals in this group.
I Indicate significant deviation from control by Donnell's test (p < .05). The increased body weight in the last group in the table (8 week expo' sure, 10/ig/kg/wcck) was considered to lie due lo the presence of ascitic fluid.
i
Sharma &. Gchring: Effects of TCDD
491
leukocytic infiltration and perivascular degeneration and necrotic changes. The incidence .oflivcr and thymus lesions in mice exposed to various levels, of TCDD for .'^nTerent xjufilions is shown in T able 2. The lesions observed in control and 0.01 pg/kg/wk TCDD-cxposcd group were minor.
Treatment-related lesions of the thymus were noted only after 4 weeks of exposure in groups given 1 or 10 ^g TCDD/kg/wcek (Table 2). The lesions observed in the thymus were primarily a reduction of the cortical area and in some cases a focal depletion of thymocytes in the cortex. Cyst formation around Hassall bodies was infrequent, and in a few cases the cortical area of thymus assumed a nodular appearance. Pyknolic thymocytes were also present.
WMH..HIMOCIMI iu he One lo the plv.,cncc ol nscihc lluiii.
T able 2
Incidence o r Discernible Lesions in the Liver a n d Thymus
of M ale M ice Exposed to TCDD*
Exposure Level
(ug/kg/week)
Organ
Duration of Exposure
2 Weeks
4 Weeks
8 Weeks
0 (Control)
Livert Thymus
V* M*
1/3 0/3
3/4 0/4
0.01
Livert 0/4 1/4
4/4
Thymus
1/4
0/4
2/4
0.1
'LiverJ
1/3 2/4
4/4
Thymus
0/4
1/4
2/4
1
Liverl 4/4 4/4
4/4
Thymus
0/4
3/4
1/4
10
LiverJ 4/4 4/4
4/4
Thymus$
1/4.
4/4 * .
0/4
"Sections examined microscopically in a blind random fashion. Only data on liver and thymus are summxriied here since kidney showed no alterations in any group. The numbers indicate the number of animals showing abnormaliiics/iota) number of animals in that
group. tThc hepatic lesions in control and those receiving 0.01 Hg/kg/week group involved
vacuolition or slight degeneration of hepatic cells. The organs showed extensive perilobular diffuse degeneration and/or necrosis. SMarkcd conical atrophy of thymus wiih or without the depletion of thymocytes w
noticed in these groups. Other groups did not show any definite lesions.
TCDD caused a stimulation of lymphocyte transformation when no mitogens were present in the culture system (F igure 1). After 4 weeks of TCDD administration, there was a significant increase in the thymidine uptake of splenic cultures ai all TCDD dose levels as compared to controls. This trend appeared to be reduced after 8
weeks of exposure. The extent of phytomilogen (PHA or PWM)-induced.lymphocyte blast formation
was reduced by TCDD exposure (FIGURE 2). The decrease in the stimulation indices (DPM in the presence of a phytomitogen divided by the DPM in an identical culture but without the mitogen) in TCDD groups is partly because of the increased thymidine uptake in unstimulaied cultures. A reduction seen in stimulation indices after 2 weeks of TCDD exposure became marked after * weeks and seemed to
492 Annals New York Academy of Sciences
disappear at 8-weck period. The decrease was observed both in PHA- and PWM.nduccd.stimulation indices, and a significant reduction (in paired comparisons) observed in one or more'dosc levels tt'different lime intervals despite the large variation inherent in this type of assay system.16
The serum immunoglobulins in mice at different periods of TCDD exposures are shown in T able 3. The treatment with 0.01 or 0.1 fi$ TCDD/kg/weck appeared to increase the immunoglobulin, while the higher doses (i.e. 1 and 10 pg/kg/wcek) of TCDD decreased these proteins.
When mice were treated orally with a single dose (10 pg/kg) of TCDD and sacrificed at 2, 4, and S weeks after the treatment, a significant increase in spontaneous lymphocyte transformation was seen only at 2 weeks after the challenge. The details of these results have been presented elsewhere.11 The effects on
DPM/MiUJon Cdti x 10'4
Pre-exposure
2-Week*
4-Week*
Duration Ot Expoture To TCDD
8-Week*
Figure I. Uptake o f `H-lhymidinc by unsttmulaied mouse splenic cultures at different periods after exposure to TCDD. Although a decrease with time is seen in control cultures, all TCDD*exposcd groups showed an increase over respective control groups. "Indicates a significant deviation from control (p < 0.05J.
lymphocyte transformation, apparent at 2 weeks post-administration persisted 21 the 4-week interval after treatment but were not significant, and no differences between control and treated animals were observed in cultures S *eeks after doing. A similar trend was observed in the respective stimulation indices. The thymic changes and the increase in liver weights also followed a similar trend. The histologic effects in liver, however, persisted, although the degenerative lesions observed microscopically were less severe after 8 weeks.
When TCDD was directly added to the media in splenic cultures, the'h mphocytes did not show any increased blastoecnic activity. In fact, 2 dose-related decrease in 3H-lhymidinc incorporation by lymphocytes was observed (FiCURE 3) with increasing TCDD concentrations. Figure * presents data on a similar system when the cells were
Sharma & Gchring: Effects of T C D D
he lymphocytes ted decrease in w*:lh increasing n the cells were
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Fk;iiIL 2. SiimiiInlion indices by pliylomilogcus, pliylobcrmgglulinin (FI IA) and poke'*ceil niiiopen (PWM) in mouse splenic cultures in relation InTCUl) exposure. The cultures arc similar In tliosc in Figure I. *Indicates significant difference in group when compared to rcspcclivc controls (p < 0.05). Slimulnlion index - DPM from a culture in lltc presence of either I'll A or PWM divided by the DI'M in n similar culture without a mitogen.
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.494 Annals New York Academv of Sciences
Table 3 Se b u m - Im m u n o g lo bu lin s is Mice Exrosro to Dif f e r en t L e v e l s or TCDD
TCDD
Exposure (#aS/Lg/wk)
Preexposure
2 Weeks
Scrum Ig i t ' 4 Weeks
8 Weeks
0 0.01 0.1 1
10
0.49 * 0.06 -- -- --
--
0.94 * 0.25
1.06 *0.11 1.04 0.15 1.17 0.27 0.87 0.13
1.14 * 0.06
1.48 * 0.16 1.67 * 0.39** 1.43 0.18 0.79 * 0.08"
0.91 0.12 1.95 0.99 2.58 * 0.47"
0.85 0.11
0.72 0.18
"The values expressed arc ratios of scrum Jg in relation to a pooled normal mouse scrum sample. Mean a S.E. of 4 observations per group.
" Indicate significant difference from the respective control at p < .05.
cultured in the presence of mitogenic agents. No effect of TCDD on stimulation indices suggests that the observation in Figure 3 was possibly due to the direct cytotoxic effect of TCDD on lymphocytes.
D iscussion
Our experiments with TCDD in mice confirm the early findings that high dose levels of TCDD are immunosuppressive. It h2S been shown to be an immunosuppres* sant in guinea pigs, and rats1 and developing rau and mice after maternal and
DPM/Millton
I i
c
i `i
*ii >v*
7 tf .4 i
In-vitro TCDD Go^ccntr*lon [M]
Figure 3. Effect of TCDD added directly to the incubation medium on lymphocyte iranjformstior. in mouse splenic lymphocyte cultures. Cells isolated from normal mice ere incubated in culture media containing appropriate coneentralions of TCDD. ` Indicates significant difference from the Cu.-.-ol cultures at p < 0.05.
I I
CCS
LrviLi or TCDD 8 Weeks
0.91 0.12
. . 1.95* 0.99
2.58 * 0 .4 7 " 0.5 * 0. - 0.72 0.18 cd norma] mouse scrum .05. TCOD on stimulation ibjy due to the direct
'.ncings that high dose be an imm unosuppres:e afie; m aternal and
icr* medium on lymphocyte from normal mice **cre
of TCDD. 'Indicaics
Sharma &. Cchcng: Effects of TCDD
595
postnatal treatm en t.4 The immunosuppression in our experiments *-3* evident by decreased stim ulation indices o f splenic lymphocytes to the mitogenic agents. PHA and PWM.
The results presented in this report, however, differ from the earlier ones in several respects. The imm unosuppressive effect of T C D D in mice was not necessarily dose-related in the ranee of concentrations that we have used. L'su2 lly the pathologic lesions were apparent, particularly in the liver, at levels of TCDD exposure lower than that were shown to be immunosuppressive. Generally the immune suppression was seen in mice at doses of 1 /ig /k g /w k or more, when exposure was continued for several weeks. At lower exposure levels, the immunosuppressive effect was not apparent while liver chances were observed. The changes in thym us, described in earlier reports'1were
Stimulton Indca
' Figure 4. Stimulation indices in splenic lymphocyte cultures incubaied in the presence of PHA or PWM and different concentrations of TCDD. The cultures are similar to those indicated in FiCL'RE 3. Stimulation index -- DPM from a culture in the presence of either PHA or PWM* divided by the DPM in an identical cuhurcwithout mitoccni. Addition of TCDD did not have any effect on stimulation indie by cither PHA or PWM.
ohcrrved in nur studies. but these were not always dose-related. O ne unique feature of such thymic lesions was the absence of any changes in the two highest dose levels of T C D D exposure at the end of 8 weeks in mice. The only appreciable atrophy of thymic cortex and depletion of thym ocytes were seen in these treatm en t levels at the end of 4 weeks. In mice, even the decrease in thymus weights that was observed after 2 and 4 weeks of TC D D exposure, was not seen after B-w-eek treatm en t. A lthough not conclusive, this finding suggests that there m ay be a recovery of thym ic tissue even if the exposure to T C D D continued at high levels. It m a y b e interpreted as a so n of adaptation in this organ to lh c presence of T C D D . Tj^c sam e was not true, however, for liver lesions, which w-erc progressive with time and also with the level of TCDD exposure.
An important observation o f this study is an increase in the spontaneous blast
496 Annals New Y o ^ Academy of Sciences
formation it] <plmfr lymphocytes without anv mitogenic inducer, This increase was
consistent fll all time periods and particularly obvious in mice receiving low dose levels
of TCDD, The exact implication of this finding ts not clear, but ii suggests a
jlimulaltoin in the functional activity of lymphocytes^ This can be compared to an
Tncrease when the animals arc challenged with an antiecn?J In cur additional studies.
Tuefi increase was seen in control groups that were injected with an antigen mixture
(tetanus toxoid and Freund's adjuvant; data not given here). One possible evoianaiion'
of this stimulation in spontaneous lymphocyte transformation may be that the
administration of TCDD produces an antigenic response, either by combining with a
'Body protein, or by causing tissue damage leading to tne release ol altered prorCins
TTiai might be antigenic, Roland and Glover1'1have reported a specific and high affinity
binding of TCDD with hepatic cytosol.
The decrease in the stimulation indices to mitogens by TCDD exposure may be the
result of immune tolerance produced by the possible antigenic effect of this chemical.
Bbth antigens and antibodies are known to produce immune tolerance or immune
unresponsivencss." In our studies, an immune unresponsivencss (or immune suppres
sion) was seen only at relatively high exposures to TCDD. which may suggest that a
saturable amount of either antigen or antibody may be present at these treatment
levels.
The hypothesis of an autoimmune response is also supported by the finding that in
mice TCDD produced an increased immunoglobulin synthesis at the low levels of
"exposure. A significant increase in total Ie appeared at A and 8 weexs alter u.T
g/kg/wcek of TCDD trejimrpt Ai fcigh
IrvrU ni TPDD (hr decrease in~
"immunoglobulin levels may be related to the damage of the organs or cells that are
sites of globulin production (e.g. lymphoid tissue).
Vos and Moore* have reported that PHA responsiveness on spicnic cells was
decreased in one-month-old mice but not in 4-month-old animals. In our studies using
4-5 month old mice (data not shown) both PHA and PW'M responsiveness were
significantly decreased 2 weeks after a single dose of 10 pg/kg TCDD, although this
decrease was not as remarkable 2S in crowing animals. In these animals as well, the
spontaneous increase in DNA synthesis was seen in splenic cultures. One of the
reasons for the relative insensitivity of adult animal lymphocytes may be that the
lymphocyte response to mitogens as well as spontaneous bias; formation in culture is
considerably decreased with age and the influence of the chemical treatment may not
be remarkable. Adult animals may also bind TCDD more efficiently in selected
organs (i.c. liver) than in the young ones, thus there may be less amount of TCDD
available in the adults in other tissues.
k-
S ummary
Male CD-I mice were orally treated with 0.01. 0.1, 1 and 10 *.- TCDD/kg body
wi./weck for up to S weeks. Random ly selected animals were sacrificed at 2. 4. and 8
weeks of exposure. An additional group was given orally 10 yg TCDD/kg and the
animals similarly sacrificed. Splenic lymphocytes from the^e animals were cultured in
vitro with or without the presence of phytomitogens. phytohemaggluiinin. and
pokeweed mitogen. The incorporation of iH-ih>midine was measured as an indication
of relative blast formation. Exposure of animals to TCDD. even at the lowest level
(0.01 H g/kg/w k for 2 weeks) caused a marked increase in the thymidine uptake by
f i i l t n r / J l y r r j p h r ^ \ - p - < T h r h l . i T i r t p r n i r r<-<.jv-irnr e\{ m i i n o r n t w- <
n: h ic h Irv rU
of TCDD exposure, indicating an immunosuppressive effect. Following a sincie
treatment with 10 pg TCDD/kg, the increase in the blast forma non was noted at 2
enees
>duccr. This increase was : receiving low dose levels rlcar, bui it suggests a
an be compared lo an . our additional studies, with an antigen mixture One possible explanation '.ation may be that the her by combining with a :ic2sc of altered proteins specific and high affinity
DD exposure may be the c effect of this chemical, ne tolerance or immune ess (or immune suppreshich may suggest that a :scnl at these treatment
,cd by the finding that in esis at the low levels of and 8 weeks after 0.1 TCDD. the decrease in organs or cells that arc
ss on splenic cells was 2Is. In our studies using y. responsiveness were 2 TCDD. although this :sc animals'as well, the : cultures. 0^e_ of the jcyies may be that the formation in culture is lical treatment may not efficiently in selected less amount of TCDD
->/# *
10 TCDD/kg body acrificcd at 2. 4, and 8
-S TCDD/kg anc the imals ere cultured in tchcmagglutinin, and isured as an indication cn zt the lowest level thymidine uptake by reduced at high levels - Following a single "ation uas noted at 2
<
i } i , 1 '| I
Sharma & Cchrnc. EfTeets of TCDD
497
weeks, the effect reduced at 4 weeks, and no difference noticed in treated vs. control 'TuTturcs 8 weeks after the treatment. Small doses of TCDD stimulate the splenic lymphpcyic transformation and this effect, although somewhat dose-related, can be reversed in a relatively short period of lime.
R eferences
1. Schewetz, B. a .. J. M. Norris. G. L. S parschu, V. K. Rowe, P. J. G ehring. J. L.
EMERSON &. C. G. G erbig. 1973. Toxicology of chlorinated dibcn20-/>-dioxins. Environ.
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