TISSUE DISTRIBUTION OF HUMAN-IGG FC-RECEPTORS CD16, CD32 AND CD64 - AN IMMUNOHISTOCHEMICAL STUDY

The tissue distribution of human IgG Fc receptors (FcgammaRs) classifi ed in three clusters of differentiation (CD16, using 5 antibodies, CD3 2, using 2 antibodies; and CD64, using 3 antibodies) was evaluated by immunohistochemistry on lymphoid (lymph node, spleen, thymus, tonsil) and non-lymphoid (heart, jejunum, kidney, liver, lung, muscle, stomach , and skin) tissues. Macrophage-like cells, including Kupffer cells, e xpressed all three classes of FcgammaR. Part of the cells coexpressed HLA-DR. Interdigitating dendritic cells that were present in high dens ity in interfollicular areas of a lymph node showing dermatopathic lym phadenopathy were immunoreactive for CD32, but not for CD16 or CD64 an tibodies. In lymphoid tissue, mantle zones of secondary follicles were labelled by CD32 and some CD16 antibodies. The immunolabelling of man tle zones was not present after washing the sections at low pH, which suggests that the molecules detected were passively absorbed on the ce ll surface (i.e. soluble FcgammaR). The immunolabelling of tonsil sect ions by various CD16 antibodies showed three patterns. The first (anti -Leu-11b) revealed labelling of solitary macrophage-like cells. The se cond (BW209/2 and 3G8) revealed, in addition, labelling of germinal ce ntres. The third (CLBgran1 and CLBgran 11) revealed labelling of solit ary cells and follicle mantles. This labelling on tissue sections was also seen in the analysis of follicular dendritic cells isolated from tonsil. The cells were faintly immunoreactive for 3G8, as well as for CD16 mAb CLBgran1, and both CD32 mAbs. In all tissues investigated the re was immunoreactivity for FcgammaRs in varying intensity on endothel ial cells of blood vessels.