Characterization of suppressor cells regulating in vitro expression of IgG2A and IgG2B antibody responses.

In vitro cooperative responses between hapten-primed anti-Thy-1.2 plus C-treated spleen cells and carrier-primed T cells have different isotypic patterns depending on the source of the T helper cells. T helper cells from primed lymph node induce IgG1, IgG2a, and IgG2b PFC responses, whereas T helper cells from primed spleen induce only an IgG1 type of response. The addition of activated spleen cells to the lymph node cells suppresses their ability to generate IgG2a and IgG2b PFC responses. The suppressor cells involved have been characterized. Functionally, they appear as nonantigen specific and isotype specific, because they never reduce the IgG1 response. They are Lyt-2.2 positive, Lyt-1 negative, and radiosensitive. Their relative resistance to anti-Thy-1.2 plus C treatment indicates that they express low amounts of this antigen or that they are heterogeneous concerning the expression of Thy-1.2.