IGG TRANSPORT ACROSS THE GUT OF THE SUCKLING OPOSSUM (MONODELPHIS-DOMESTICA)

We investigated IgG transport across the gut of suckling opossums to s ee whether it is likely to be Fc gamma R-mediated. Enterocytes isolate d from the proximal and distal regions of the small intestine of suckl ings aged 12-52 days, and reacted with indicator SRBC at pK 6.0 or 7.2 , bound opossum IgG in rosette assays. Considerable overall variation was observed in the numbers of enterocytes forming rosettes. No bindin g was seen with rabbit IgG at these ages, or with opossum and rabbit I gG when enterocytes were obtained from opossums aged 55-73 days. Oposs um anti-SRBC antibody (IgG) fed to sucklings at 52 days and earlier (b ut not later) could subsequently be detected in the serum. However, ra bbit anti-SRBC antibody (IgG) could not be detected in the blood serum when fed to sucklings of any age. Fluorescent tracing of FITC-labelle d opossum and rabbit IgG fed to suckling opossums, and of endogenous o possum IgG, pointed to transport of the homologous IgG occurring acros s gut enterocytes of the proximal region. These results suggest that I gG is recognised and transcytosed by specific Fc gamma Rs present on o possum enterocytes prior to weaning.