IMMUNOLOGIC STUDIES WITH INTRINSIC FACTOR IN MAN*

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Abstract
Two patients with pernicious anemia were immunized with purified hog intrinsic factor concentrate (HIFC) by repeated injection. Both developed skin reactivity of the immediate type and precipitating serum antibodies demonstrated by immuno-electrophoresis. Nevertheless neither patient became refractory to orally administered HIFC and continued to absorb C06O-B12 normally whenever it was fed with HIFC. Postimmunization sera from both patients closely resembled rabbit anti-HIFC sera in their ability to (1) precipitate HIFC in agar diffusion systems, (2) prevent the electrophoretic migration of a Co57-Bi2-HIFC complex, (3) suppress the HIFC-enhanced uptake of vitamin B12 by liver homogenates, and (4) inhibit vitamin B12 absorption, when administered orally with HIFC, in one of the two subjects with pernicious anemia. It is concluded that the refractory state is mediated by local factors within the gut rather than by circulating antibodies.