Lysolecithin analogs as adjuvants in delayed-type hypersensitivity in mice. II. Studies on the mode of action

Lysolecithin analogs (LLA) possess adjuvant activity in delayed-type hypersensitivity (DTH). To elucidate their mode of action, we studied the influence of LLA on the recruitment of hemopoietic progenitor cells and on the induction and transfer of DTH. Whereas the number and composition of colony-forming cells (CFC) in the bone marrow remained unaltered in LLA-treated mice, the number of CFC in the spleen was augmented severalfold, and the content of macrophage progenitors was remarkably increased. DTH was induced with macrophages from peritoneal cells (PC) pulsed with keyhole limpet hemocyanin (KLH). A more marked DTH response was obtained with KLH-pulsed PC from LLA-treated mice than from mice given phosphate-buffered saline (PBS). On the other hand, there was no difference in the DTH response following adoptive transfer of sensitized cells to naive mice pretreated either with PBS or LLA. It is concluded that the adjuvant effect of LLA can be accounted for partly in terms of their effects on macrophage progenitors and partly in terms of a more effective T cell activation by antigens associated with LLA-derived macrophages.