Bl. Granger et Sj. Warwood, RAPID INTERNALIZATION AND DEGRADATION OF SURFACE-BOUND ANTIBODIES BY TRITRICHOMONAS-FETUS, The Journal of parasitology, 82(4), 1996, pp. 539-549
Tritichomonas foetus is a protozoan parasite of cattle that can be cul
tured axenically. Three monoclonal antibodies specific for surface ant
igens of T. foetus were found to be rapidly internalized and degraded
by these cells after binding. Degradation was not due to secreted or a
rtificially liberated proteases but depended on targeting to internal
degradative compartments. Radiolabeled catabolites of the antibodies w
ere subsequently incorporated into the parasite's own proteins. Antibo
dy degradation could be inhibited by certain protease inhibitors or lo
wered temperatures; a sharp reduction in degradation between 20 C and
15 C was similar to a well documented block in endocytic transport to
degradative compartments of mammalian cells. Growth and proliferation
of T. foetus in the continuous presence of the antibodies appeared unh
indered, but there was a general shift toward expression of both more
and less of each epitope among cells within each population. Subclones
of these populations always exhibited striking variability in epitope
expression levels, with patterns similar to the parent cultures. Thes
e findings may lead to a better understanding of how T. foetus resists
host immune responses.