NATURAL AND ACQUIRED-RESISTANCE TO LEISHMANIA - CELLULAR ACTIVATION BY LEISHMANIA-AETHIOPICA OF MONONUCLEAR-CELLS FROM UNEXPOSED INDIVIDUALS IS THROUGH THE STIMULATION OF NATURAL-KILLER (NK) CELLS

Cells from normal non-Leishmania-exposed individuals could respond in vitro by proliferation and interferon-gamma (IFN-gamma) production to Leishmania aethiopica stimulation. The main cell type that appeared to be activated following such stimulation was CD3(-), CD16(+)/56(+), i. e. NK cells. Of the few CD3(+) cells responding, an involvement of CD8 (+) cells was evident in the absence of activation of CD4(+) cells in normal individuals, while a different feature was observed when patien ts' cells were investigated. Cells from patients with L. aethiopica in fection did not show this NK response, but rather the CD4(+) cells wer e the prominent responding cells. No evidence of the involvement of su perantigens or cells utilizing the gamma delta T cell receptor (gamma delta cells) in the response of unexposed individuals was noted.