Regulatory role of FcR+ and FcR- monocyte subsets in Mycobacterium leprae-induced lymphoproliferative response in vitro.

We investigated nine rhesus monkeys (Macaca mulatta) inoculated with Mycobacterium leprae and three normal human contacts. Peripheral blood monocytes were separated into Fc receptor positive (FcR+) and Fc receptor negative (FcR-) fractions, and their regulatory role in the lymphoproliferative response in vitro to M. leprae was studied. FcR- monocytes had strong antigen presentation activity and produced no suppressor effect while FcR+ monocytes had weak antigen presentation activity and produced a non-specific suppressor factor spontaneously. With this assay system we determined that M. leprae-inoculated rhesus monkeys could be divided into three groups: good responders, very weak responders, and non-responders.