Enzymatic activation of immunoglobulin binding factor in female reproductive tract.

Human seminal plasma and cervical mucus contains an immunoglobulin binding factor (IgBF) which interacts with IgG as monomers under reducing condition. It may play a role in preventing antibody production against allogeneic sperms in the female reproductive tract. However, since IgBF is secreted as a homodimer that does not bind IgG, in vivo activation systems should be investigated. GSH reduces the inactive native dimer to the active monomer. Protein disulfide isomerase (PDI), a molecular chaperone, alters the configuration of dimers to active monomers. 20S proteasomes produced by activated T cells which cleave the dimers in the presence of GSH to active fragments. All these activating systems are widely distributed as cellular enzymes in vivo. Also PDI mRNAs are expressed in uterine cervix, endometrium and fallopian tube. Since these enzymes are produced upon stimulation by the immune system, we hypothesize that immunocompetent cells interact with allogeneic sperms, leading to the local production of these enzymes that will activate IgBF.