Schistosomiasis mansoni in baboons. VI. Plastic-adherent-cell suppression of the primary in vitro antibody response of peripheral blood mononuclear cells to a heterologous antigen (SRBC) during chronic infection.

Peripheral blood mononuclear cells (PBMC) from five of six baboons (Papio cynocephalus) with chronic schistosomiasis mansoni showed a marked reduction in the ability to generate anti-sheep erythrocyte (SRBC) plaque-forming cells (PFC) after primary in vitro immunization as compared to the PFC responses of PBMC from normal (non-infected) baboons. Removal of the plastic-adherent (PLAD) cells from the PBMC of these animals results in a population of cells capable of responding to in vitro immunization with SRBC at a level equal to or higher than their normal counterparts. Reconstitution of plastic-non-adherent cells with PLAD cells re-establishes suppression. In contrast, the single apparently non-suppressed infected baboon showed reduced responses after PLAD cell removal, but, upon reconstitution with PLAD cells, responses were higher than those obtained before cell separation. No evidence of PLAD suppressor cells in normal animals was found, and indeed the data suggest that PBMC from normal animals may require a PLAD accessory cell for full responsiveness.