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Tumor-specific antigens of a guinea pig hepatoma induced by diethylnitrosamine were detected by the inhibition of migration of specifically sensitized macrophages from capillary tubes, and by the local passive transfer of delayed skin hypersensitivity and the suppression of growth of intradermally same injected tumor.

The Forssman antigen content of diethylnitrosamine-induced guinea pig hepatomas was found to be greater than that of either autogenous or allogeneic guinea pig liver. The autogenous normal liver was obtained from guinea pigs before tumor induction, and comparison of normal and neoplastic tissues was based on the capacity of these tissues to inhibit (absorb) the hemolytic activity of rabbit antitumor serum. A method is presented for distinguishing quantitative from qualitative antigenic differences in the search for tumor-specific antigens. The results of these experiments indicate that, in the absence of strict quantitation, quantitative differences may be mistaken for qualitative differences.

Isolated segments of human colon and to a lesser extent ileum were capable of synthesizing hemolytically active C'1. This conclusion was based on the following evidence: After elimination of C'1 from tissue with EDTA, we found that segments of the intestinal tract in short-term organ culture showed a 50-1000-fold increase in C'1 activity. The rate of production of C'1 in human intestine was highly temperature dependent; C'1 production was reversibly inhibited by puromycin and actinomycin D. Furthermore, (14)C-labeled amino acids were incorporated into molecules which behaved like C'1. No significant C'1(hu) synthesis was observed in isolated segments of jejunum, stomach, liver, kidney, lung, spleen, lymph node, and thymus.

The mechanism of complement fixation on cell surfaces by whole antiserums, and by 19S and 7S fractions has been studied with a new comple-ment-fixation test. This test is based on the fixation and transfer of the activated first component of complement (C1a). We have concluded that a single molecule of 19S antibody in combination with antigen at the cell surface is sufficient to bind one molecule of C1a. For 7S antibodies at least two molecules in close proximity at the cell surface are required to fix one molecule of C1a.

Interaction of a phospholipase C (from Clostridium welchii) preparation with the first component of human and guinea pig complement in serum is due to contaminants devoid of phospholipase C activity.

Sex hormones influence the hemolytic of one or more of the late-acting components of complement measured in the presence of trisodium ethylenediaminetetraacetate. The titers of the serums of male mice, normally tenfold higher than those of females, fell after castration, becoming about the same as those of females. The titers of the serums from females rose after these mice were castrated, but castration did not affect the activities of the first, second, and fourth components of complement. Serums of normal and castrated mice of both sexes treated with testosterone showed increased late-acting component activity, whereas the estrogen caused decreased activity. Treatment in vitro of mouse serum with these hormones had no effect on the activity of late-acting components.