Tolerance of Erythrocytes in Poultry: Loss and Abolition.

Fowls which tolerate foreign erythrocytes, but which have not received a transplant of variable cells, eventually lose tolerance when the supply of erythrocytes is discontinued. The loss follows, at an interval, after the foreign erythrocytes have been eliminated by the normal mechanism for removal of aged cells; earlier loss can be brought about by eliminating the foreign cells with passive antibody. The interval required for loss varies, for tolerance of homologous erythrocytes, from less than 5 to over 215 days. The age of the tolerance bird, and hence the duration of exposure to antigen, is the main factor influencing the interval required; the preceding level of tolerance exerts comparatively little effect. An attempt to terminate tolerance by adoptive immunization was only partially successful. [ABSTRACT FROM AUTHOR]