SOLUBLE FC-GAMMA-RIII (CD16) AND IMMUNOGLOBULIN-G LEVELS IN SEMINAL PLASMA OF MEN WITH IMMUNOLOGICAL INFERTILITY

Receptors for the Fc region of the immunoglobulin G (IgG) (Fc gamma R) have been recognized as a link between humoral and cellular immune re sponses. A soluble form of FcgammaRIII (CD16) has been found in semina l plasma (SP), which may modulate immunosuppression of antisperm immun e responses in the male and female reproductive tracts. SP from some i ndividuals apparently have lower levels of FcgammaRIII, but it is not known whether the diminished activities are due to low receptor concen tration or steric interference from IgG. To test the hypothesis that d ifferent levels are due to steric interference, relative levels of Fcg ammaRIII were measured in SP using monoclonal antibody 3G8 in an ampli fied enzyme-linked immunosorbent assay (ELISA) system. Men who were po sitive for antisperm antibodies (ASA) by Sperm Mar and direct immunobe ad assay (N = 26) and negative for ASA (N = 26) were tested. Individua ls who were ASA positive had lower detectable levels than those who we re ASA negative (t = 1.99, P = 0.05). Therefore, variation in FcgammaR III levels may be due to steric interference from IgG. IgG subclaSS co ncentrations in SP of both groups were determined using an ELISA metho d and compared to FcgammaRIII levels. Slight correlations were seen fo r IgG1 (r2 = 0.237, P < 0.001), IgG2 (r2 = 0.204. P < 0.001), and tota l IgG (r2 = 0.299, P < 0.001) in relation to FcgammaRIII levels in ASA -negative SP specimens. We conclude that ASA-positive SP has lower det ectable levels of FcgammaRIII and that some variability in ASA-negativ e SP can be attributed to variance in IgG subclass levels, especially IgG1 and IgG2. Therefore, we can conclude that lower levels of Fcgamma RIII in some SP specimens are due to steric interference from IgG.