IMMUNOLOGICAL ENHANCEMENT BY MOUSE ISOANTIBODIES - IMPORTANCE OF COMPLEMENT FIXATION

Abstract

Balb/c anti-EL 4 [C57B1 leukemia] serum was separated into 7 fractions of increasing electrophoretic mobility by gradient elution from a column of DEAE-cellulose. The 1st 4 fractions, containing the bulk of the immunoglobulins, were tested for their effects in vivo on the growth of EL in Balb/c mice. The 1st fraction, which contained most of the cytotoxic activity in vitro, produced inhibition of growth, while the 3rd fraction produced enhancement. The activities of F (ab[image])2 and Fab[image] fragments from A strain anti-E.L.4 serum were also studied. Both preparations lost cytotoxic activity on EL4 cells in vitro, but were capable of blocking the effect of undigested Ig[immunoglobulin]G. F(ab[image])o retained hemagglutinating activity on C57B1 red cells, whereas Fab[image] did not. Fab[image] was able to block the hemagglutinating effect of undigested IgG and F(ab[image])2- Both F(ab[image]), and Fab[image] could produce enhance ment of the growth of EL4 in A strain mice. Non-complement-fixing antibodies may be critical in the production of enhancement.