ACTIVATION-DEPENDENT EXPRESSION OF LOW-AFFINITY IGG RECEPTORS FC-GAMMA-RII(CD32) AND FC-GAMMA-RIII(CD16) IN SUBPOPULATIONS OF HUMAN T-LYMPHOCYTES

Receptors for IgG (Fc gamma R) are expressed by small subpopulations of peripheral blood T lymphocytes. Our studies demonstrate that T lymphocytes can be induced in vitro to express two different low-affinity Fc gamma R. Mitogen activation of peripheral blood T lymphocytes obtained from eight healthy individuals leads to considerable augmentation of the Fc gamma RII(+) (CD32)T cell subpopulation. The highest percentage of CD32 expressing T lymphocytes could be detected after three days of activation. The T cell subpopulation, which transiently express the CD32 antigen, encompasses CD4(+) and CD8(+) cells. Molecular cloning of the CD32 antigen by reverse transcription and polymerase chain reaction demonstrates that activated human T lymphocytes express the Fc gamma RIIb2 isoform. The percentage of the Fc gamma RIII(+) (CD16) T cell subpopulation was significantly increased only in the lymphocyte populations obtained from three out of eight volunteers immediately after mitogen activation. However, during short-term cell culture the CD16 expressing CD8(+) T cell subset increased in the T cell population from all individuals investigated. During this time, the IL-2 receptor alpha-chain (CD25) expression level decreased as a function of time. In contrast to the CD8(+)CD16(+) T cells, the percentage of the non-MHC-restricted CD56(+)CD16(+) T cells was not influenced by mitogen activation and time of cell cultivation. We could show that CD16 in T cells is able to mediate a stimulus leading to proliferation of the CD8(+)CD56(-)CD16(+) T cells but not that of the CD56(+)CD16(+) T cell subset. This discrepancy cannot be explained by the expression of different Fc gamma RIII isoforms, because both T cell subsets express FcyRIIIA alpha, as we demonstrate in this report.