Generation of CFU(C) suppressor T cells in vitro: VII. T derived colony inhibitory activity (Td/CIA) has no suppressor effect on in vitro immunoglobulin production

T derived colony inhibitory activity (Td/CIA) was obtained from unstimulated T cells from aplastic anemia patients (SAA), or from PWM primed normal T cells. Td/CIA suppressed CFU(C) growth of normal allogeneic marrow to less than 30% of expected growth. Td/CIA was then added to normal peripheral blood T and B cells, printed with PWM, to test whether it would interfere with in vitro immunoglobulin (Ig) production. When Td/CIA from normal T cells was added to cultures of T + B cells + PWM there was a 2-2.1-fold increase in Ig production. Similarly the addition of Td/CIA from SAA patients also resulted in a 1.4 up to 166-fold increase in Ig production. These results indicate that either (a) the targets for Td/CIA are expressed on hemopoietic but not on T and B cells, or (b) that Td/CIA inactivates an accessory cell which is essential for CFU(C) growth but not for the PWM driven in vitro B cell differentiation system.