Modifications in the handling in vitro of 125I-labelled keyhole limpet haemocyanin by peritoneal macrophages from mice pretreated with the adjuvant Corynebacterium parvum.

Peritoneal macrophages were isolated from C. parvum-pretreated (CP) and normal CBAT6T6 mice and their in vitro handling of 125I-labelled Keyhole limpet haemocyanin (125I-labelled KLH) studied in relation to the humoral anti-KLH responses induced in corresponding animals. CP pretreatment exerted an adjuvant effect on the production of anti-KLH antibodies, both IgM and IgG, which was also demonstrable with a normally subimmunogenic dose of antigen. There was a clear difference between the handling of 125I-labelled KLH by CP and normal macrophages. The initial uptake of the antigen by CP macrophages was slower than that by normal ones. Moreover, 125I-labelled KLH was degraded to a lesser extent within CP macrophages, although the rates of antigen digestion were similar in both kinds of cells. The lower extent of 125I-labelled KLH degradation within the CP macrophages was due to a larger amount of antigen being retained on the cell membrane, where it escapes digestion. The findings suggest that intensified presentation to lymphocytes of antigen on the macrophage surface could be a causal factor in the adjuvant action of CP.