INHIBITION OF MITOGEN-INDUCED LYMPHOCYTE PROLIFERATIVE RESPONSES BY TRICHOSANTHI~

H. W. Yeung and S. P. Poon Department o f B i o c h e m i s t r y and Chinese Med ic ina l M a t e r i a l Resea rch C e n t e r , Chinese

U n i v e r s i t y o f Hong Kong, S h a t i n , N.T°, Hong Kor~.

Modula t ion by t r i c h o s a n t h i n (TC3), a p u r i f i e d p r o t e i n o b t a i n e d from t h e Chinese d rug , T ianhua fen ( T r i c h o s a n t h e s k i r i l o w i i ~ , o f t h e c o n c a n a v a l i n A (con A) and l i p o p o l y s a c c h a r i d e (LPS) s t i m u l a t e d murine s p l e n o c y t e p r o l i f e r a t i o n in v i t r o was s t u d i e d . R e s u l t s showed t h a t i n c u b a t i o n o f t h e normal s p l e n o c y t e p r o l i f e r a t i o n induced by bo th mi togens in a d o s e - d e p e n d e n t manner. The e f f e c t was not due to c y t o t o x i c i t y , s i n c e v i a b i l i t y e x p e r i - ments showed no s i g n i f i c a n t d e c r e a s e in v i a b i l i t y [ o r t h e c o n c e n t r a t i o n s o f TC3 used . I t was concluded t h a t t h e immunosuppreesive p r o p e r t i e s o f t h e aqueous e x t r a c t o f t h e Chinese d rug , T i a n h u a f e n , p r e v i o u s l y no ted a r e due to t h e d i r e c t s u p p r e s s i v e e f f e c t o f TCS on lymphocytes a n d / o r s a c r o p h a g e a .

EFFECTS OF PROSTAGLAN~INS AND LOW DOSE IRRADIATION ON HlgdAN T LYMPHOCYTE SUBPOPULATIONS

N. Gualde and J.S. Goodwin Department of Medicine, University of New blexico School of Medicine, Albuquerque, New Mexico, 87131 USA.

PTostaglandins and ionizing irradiation are well known imaunosuppressors in vivo and in vitro. We have observed that under some particular conditions PGE2 and RX can enhance the proliferative response of human lymphocytes in vitro. 1. Onfractionated human T cells or T cell subsets separated by means of a monoclonal antibody rosetting technique were stimulated by conA or PHA after overnight incubation. Lectins and PGE2 were added to the culture after the preincubation and it was observed that the proliferative response of the OKT8(+} subset (isolated with either positive or negative selection) was enhanced but the OKT4(+) subset was inhibited. 2. When the fresh or the preincubated T cells or T cell subsets received low doses of irradiation (25R to IOOR) and were stimulated by PHA or conA without the presence of prostaglandins, the thymAdine uptake was always increased with the OKT8(+) subset and decreased with the OKT4(+) and Ok~5(+) subsets. 3. Our data suggests that PGE and low dose RX, which are both known to inhibit cellular immune responses, may work by stimu.lating suppressor cells.

THE TEMPORAL RELATIONSHIP BETWEEN PREDNISOLO~ TREATMENT AND THE DEGREE OF I~HIBITION OF MIXED LYMPHOCYTE REACTION.

See Y. T6o.~j =.d Lc6t.~e Z. ~,e~ ~partment of Pharmacy, University of California, San Francisco, CA 94143 We examined the sensitivity of human peripheral blood lymphocytes (PBLs)to prednisolone (P) at various stages of immunologlc activation in the mixed lymphocyte reaction (MLR). Micro 2-way MLPus were cultivated in the presence of 15Z pooled human serum spiked with dif- ferent concentrations of P and harvested on day 3. P's inhibitory activity was found to be strongly dependent upon the period in which it is present in the MLR. While pretrearJnent for up to 30 hrs has no significant effect on the MLR, delays in its addition or its early removal from the ~ decrease the P effect. The same results were obtained at all doses tested (25-1000 ng/ml). Even a relatively brief delay of 2.5 hrs caused a significant de- crease, averaging 18.4+5.5Z, in thePeffect. Delays of 14 and 30 hrs dimlnishedP's effect by 51.6+19.3% and 78.~17.9%, respectively. Similarly, removal ofP (250ng/ml) after 5 hrs o~Incubatlon decreased the drug effect by more than 70Z, while its removal after 30 hrs has little, if any, effect on its overall inhibitory action. These results indicate that P acts by interfering with early stages of the allogeneic response. PBLs, while re- latively insensitive to P before antigenic stimulation, are extremely sensitive to P's inhibitory effect when activated. This sensitivity, however, decreases with time and disappears shortly, after about 30 hrs.

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