IGG-FC RECEPTORS IN STRATUM GRANULOSUM - AN IMMUNOLOGICAL DEFENSE IN HUMAN SKIN

Receptors for the Fc-part of IgG (Fc tau R) in stratum granulosum of n ormal human skin were examined using cryosections and indirect immunof luorescence staining with 1) soluble immune complexes and 2) monoclona l antibodies (MoAbs) against different types of Fc tau R, i,e, 32.2 (a nti-Fc tau I-CD64), IV.3 (anti-Fc tau RII-CD32) and Leu 11b (anti-F ta u RIII-CD16). The immune complexes gave staining corresponding to stra tum granulosum in sections from all skin specimens. Inhibition experim ents showed that pre-incubation of the sections with monomeric and hea t-aggregated human IgG, periodic acid and formaIdehyde inhibited the i mmune complex binding, F(ab')2 containing immune complexes did not bin d to the skin sections. The MoAb 32.2 gave granular and Leu 11b linear staining corresponding to stratum granulosum. In addition, both IC, 3 2.2 and Leu 11b gave weaker staining of keratinocytes in other parts o f the epidermis. IV.3 stained epidermal Langerhans' cells and were unr eactive with other epidermal cells, Indirect immunofluorescence staini ng with MoAbs against IgG subclasses showed the presence of all IgG su bclasses in stratum granulosum. The results show that granulosum cells express both high- and low-affinity IgG receptors and in vivo bound I gG. The data point to a role for stratum granulosum in cutaneous immun ity.