Necessity for interaction between adherent and non-adherent rat spleen cells for the generation of a suppressor factor of NK activation.

Whole rat spleen cell populations in culture release constitutively a factor which suppresses the NK activation in response to interleukin-2. Culture supernatants derived from adherent (AD) and non-adherent (NAD) cell preparations obtained from rat spleen cells, did not have a suppressor activity comparable to that present in the culture supernatants of whole spleen cells. When reconstituted mixtures of the AD and NAD cells were cultured, high levels of suppressor activity could again be demonstrated in the culture supernatants, indicating that some kind of co-operation between AD and NAD cells was needed for efficient generation of the suppressor. Non-suppressive culture supernatants derived from NAD cells became suppressive when AD cells were cultured in them. On the other hand, relatively little suppressor activity was generated when NAD cells were cultured in non-suppressive culture supernatants from AD cells. Our results seem to indicate that NAD cells may release some agent which is not itself a suppressor but either (a) induces the generation of suppressor activity from AD cells, or (b) is "processed" into a suppressor agent by AD cells.