Effector-cell blockade. II. A demonstration of the reversible masking of an immune response by blockade of antibody-forming cells

Previously we showed that multivalent forms of antigen could specifically block the effective secretion of antibody by binding to the antibody‐forming cell (AFC). We termed this inhibition of antibody‐secretion at the level of the AFC “effector cell blockade” (ECB). The present paper shows that dinitrophenylated gelatin, (DNP‐GEL), can induce ECB in vitro. Thus, portions of a suspension of spleen cells from DNP‐immune mice were incubated for 30 min with DNP‐GEL, washed and then assayed for anti‐DNP‐plaque‐forming cells. The resultant plaques were much fewer and smaller than those in assays of control portions of the spleen cell suspension. This DNP‐GEL‐induced ECB was shown to be reversible by treatment of the DNP‐GEL‐incubated cells with the specific enzyme collagenase. The reversibility of ECB by removal of extracellular antigen was confirmed using the multivalent antigen DNP‐glucan, together with the enzyme β‐lichenase, an enzyme with no action on mammalian carbohydrates. The in vitro response to dinitrophenylated polymerized flagellin could be inhibited by the addition of DNP‐GEL at any time during the culture period. However, after the early hours of culture, the inhibition caused by the addition of DNP‐GEL was totally reversible by treatment of the cells with collagenase after harvest and immediately prior to assay. This demonstrated that B cells could divide and differentiate to AFC, despite the presence of multivalent forms of specific antigen in concentrations sufficient to block, by ECB, the detection of a response using a hemolytic plaque method. The demonstration that persistent, multivalent antigen can produce a state of apparent unresponsiveness in spite of the presence of an ongoing immune‐response suggests that the importance of a reversible masking of an immune response by ECB should be evaluated in all models of tolerance using this class of antigen.