Characterization of protein phosphorylation by 2,3,7,8-tetrachlorodibenzo-p-dioxin in murine lymphocytes: indirect evidence for a role in the suppression of humoral immunity.
Studies were undertaken to more thoroughly characterize 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced stimulation of kinase activity in murine lymphocytes. In female B6C3F1 mice, TCDD-induced phosphorylation of 29, 45, 52 and 63 KDa proteins was selective for B cells, with little or no enhancement observed in T cells. When B cells were purified and separated by density on a percoll gradient, phosphorylation was only observed in the band composed of activated B cells, and was not enhanced in the band composed of resting B cells. TCDD-stimulated phosphorylation was associated with both the cytosol (45 and 52 KDa species) and membrane (52 KDa species) fractions. Purified B cells from both DBA/2 (Ahdd) and C57B16 (Ahbb) mice demonstrated equivalent enhancement of phosphorylation in response to TCDD. Administration of human gamma interferon (Hu-IFNg) at concentrations from 0.5 to 500 Units/ml produced a dose-related reversal of TCDD-induced suppression of in vitro antibody responses to both the polyclonal B cell activator, LPS, and the T-dependent antigen, sRBC in whole splenocytes isolated from female B6C3F1 mice. These concentrations of Hu-IFNg did not affect the magnitude of either response in the absence of TCDD, and did not reverse dexamethasone-induced suppression of either in vitro antibody response. TCDD-induced suppression of the T-dependent response was reversed only when Hu-IFNg was added to culture within the first 18 hours after treatment with TCDD and sRBC. These studies demonstrate that Hu-IFNg can reverse TCDD-induced in vitro Ab response suppression if it is administered during the period of susceptibility to TCDD. TCDD-induced phosphorylation in isolated B cells was also antagonized following co-incubation with Hu-IFNg. The profile of TCDD-induced increases in protein phosphorylation, including the selective effect on activated B cells, the general involvement of both cytosolic and membrane proteins, the lack of segregation with the Ah-dependent processes, and the ability of Hu-IFNg to reverse both the suppression of the Ab response and the increase in phosphorylation, supports the interpretation that such phosphorylation is involved in TCDD-induced suppression of the Ab response.
Snyder
N K
NK
Department of Pharmacology and Toxicology, Medical College of Virginia/Virginia Commonwealth University, Richmond 23298.
Kramer
C M
CM
Dooley
R K
RK
Holsapple
M P
MP
D000818:Animals; D000917:Antibody Formation / Q000187:drug effects*; D001402:B-Lymphocytes / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D005260:Female; D006801:Humans; D007166:Immunosuppressive Agents / Q000037:antagonists & inhibitors / Q000633:toxicity*; D008214:Lymphocytes / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D010766:Phosphorylation / Q000187:drug effects; D000072317:Polychlorinated Dibenzodioxins / Q000037:antagonists & inhibitors / Q000633:toxicity*; D011506:Proteins / Q000187:drug effects*; D013154:Spleen / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology / Q000378:metabolism
D007166:Immunosuppressive Agents; D000072317:Polychlorinated Dibenzodioxins; D011506:Proteins