Auto-Sensitization of Trypsin Treated Human Red Cells by Complement. ∗

Abstract

Comment and summary. The foregoing data indicate that trypsin treated human RBC become sensitized with complement (C′) during 37°C incubation with the autologous (or homologous) fresh serum of normal donors. This C′sensitization appears to be mediated by a distinct serum factor, “Tr. factor.” The greater sensitizing activity of sera from certain patients with “autoimmune” hemolytic disease (AHD) is probably attributable, in the main, to the presence in these AHD sera of a larger quantity of the same Tr. factor found in normal sera. If so, the combined evidence from studies of normal and AHD sera would suggest that Tr. factor is an acquired, normally occurring, C′-fixing 19s y-globulin active against proteolytically altered RBC over a broad thermal range. The Tr. factor appears to be distinct from the more familiar types of C′-fixing antibodies reactive with unaltered autologous RBC, such as anti-I cold agglutinin and anti- H “incomplete” cold antibody.

Many other workers have described factors in the sera of normal donors(9-12) or of some AHD patients(l3,14) capable of agglutinating, lysing or sensitizing trypsinized RBC. Indeed, quite analogous observations have been made with RBC altered by proteases other than trypsin or by other chemical treatments. To our knowledge, demonstration of the induction of C′ sensitization of the RBC in such systems has not been previously reported. The trypsin treatment employed in the present study was generally milder than that commonly used in other investigations. It seems likely, however, that our Tr. factor is the same as the factors studied by Jankovic(l1) and by Yachnin and Gardner (12). The spontaneously reversing agglutination of trypsinized RBC described by Rosenthal and Schwartz (9), on the other hand, may represent a distinct phenomenon. The present observations should not be confused with the well known enhancement of antiglobulin reactions produced by treating already sensitized RBC with proteases(15).