Regulation of delayed‐type hypersensitivity. IV. Antigen‐specific suppressor cells for delayed‐type hypersensitivity induced by lipopolysaccharide and sheep erythrocytes in mice

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Abstract
Mice injected subcutaneous with 1 × 108 sheep red blood cells (SRBC) developed high levels of delayed-type hypersensitivity (DTH) to SRBC 4–8 days after injection. Such DTH was suppressed when 100 μg lip polysaccharide (LPS) was injected intravenously 1–2 days before or at the time of SRBC injection. This suppression of DTH was transferable by spleen, lymph node, thymus and bone marrow cells to sensitize or normal syngeneic recipients, but could not be transferred by serum. Suppressor cells were not induced by LPS alone or SRBC alone, and they were antigen-specific since DTH to chicken red blood cells was not affected. The suppressor cells appeared in the spleen in optimum number 3–4 days after induction. They were theta-negative and Ig-positive as judged by antiserum plus complement treatment and by Ig rosette separation. Attempts to obtain soluble suppressor factor from the suppressor cells by sanitation or in vitro incubation were unsuccessful. Mitomycin C treatment of the suppressor cells completely abolished the suppressor activity. Thus, LPS, in conjunction with antigen, appears to induce a population of specific suppressor B cells which are capable of regulating T cell function.