Immunohistochemical identification of factor X-like antigen in the A cells of the normal human pancreas.

An indirect immunofluorescence technique using two rabbit anti-human factor X sera was used to investigate the presence of factor X in various human tissues. Of all tissues studied only the cytoplasm of some islet cells of the six human pancreases illustrated specific reactivity for factor X-like material. No reaction was seen in the exocrine pancreas. Cross-absorption studies with factor X-deficient plasma, glucagon or alpha-1-antitrypsin did not modify the pattern. On the contrary, cross-absorption with factor X Friuli or with normal plasma eliminated the positivity. No factor X-like material was seen in rat or guinea pig pancreas. The double-immunofluorescence technique demonstrated that the reactivity was localized only in the cytoplasm of the A cells.