MICROVASCULAR PERMEABILITY TO THE F(AB')(2) FRAGMENT OF IGG IN THE MALE-RAT REPRODUCTIVE-TRACT AT PUBERTY

Development of contraceptive vaccines has recently raised much interes t following the cloning of the sperm and oocyte components involved in the sperm-oocyte interaction. The main difficulty of immunocontracept ion in the male is the poor access of antibodies to the luminal compar tment. As recent literature suggests that many substances are transpor ted to the testis by receptor-mediated or fluid-phase transcytosis, th e dependence of the transport of IgG on the F-c receptor was studied i n the present investigation by comparing the penetration of whole IgG and the F(ab')(2) fragment of IgG to the testis and epididymis. The ma ximum volume of distribution (V-eq) for the F(ab')(2) fragment was sig nificantly higher than that for whole IgG in the testis of 30-60-day o ld rats, in the caput and cauda of 30- and 45- day old rats and the co rpus of 45-day old rats. The speeds at which equilibrium between tissu e extracellular fluid and serum was reached (K) for the F(ab')(2) frag ment and whole IgG were significantly different in the testicular caps ule of the 60-day old, in the caput and corpus of the 45- and 60-day o ld and in the cauda of the 45-day old rats. The microvascular permeabi lities (PE) to the F(ab')(2) fragment were more than 2-fold higher tha n those to whole IgG in the testis of the 20-, 45- and 60-day old, in the testicular capsule of the 20- and 45-day old, in the caput of 20-, 30- and 60-day old and in the corpus of 20-day old rats. The PE to wh ole IgG was more than 2-fold higher than that to the F(ab')(2) fragmen t in the cauda of the 45-day-old rats. The PE to the F(ab')(2) fragmen t increased steadily from 20 to 60 days of age in the testis and caput , but in the corpus there was a more abrupt increase between 30 and 45 days of age. In the cauda, PE remained in the same range of magnitude throughout pubertal development. These results suggest that the F(ab' )(2) fragment reaches the lumen of the reproductive tract more easily than whole IgG from 30 days of age onwards in the testis, whereas in t he caput, corpus and cauda epididymidis the rate at which F(ab')(2) fr agment reaches the lumen increases only temporarily at the time of app earance of spermatozoa in the lumen. Transport of IgG to the male repr oductive tract is thus unlikely to be mediated by F-c receptors. (C) 1 997 Elsevier Science Ireland Ltd.