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The immunosuppressive effect of an alpha globulin fraction isolated from normal human plasma is described. The administration of this material to rats suppressed both the primary and secondary antibody responses against sheep erythrocytes. Alpha globulin also depressed the ability of mice spleen cells to confer immunity to irradiated isologous recipients. The in vitro addition of alpha globulin to mouse peritoneal leucocytes (MPL) and whole human blood caused a significant reduction of their phagocytic activity against bacteria. The mode of action of alpha globulin in relation to its immunosuppressive activity is discussed. [ABSTRACT FROM AUTHOR]

Methods have been devised to significantly alter the phospholipid composition of LM cells grown in serum-free tissue culture medium. The polar head groups of the phospholipids, as well as the acyl groups of these lipids, can be changed. When LM cells were grown in medium containing choline analogues, either N-methyl-ethanolamine or N,N-dimethylethanolamine, or the unnatural analogues, 1-2-amino-1-butanol or 3-amino-1-propanol, up to 50% of the cellular phospholipids contained the analogue supplied. When linoleate was added to the cells as a bovine serum albumin complex, up to 40% of the fatty acids of the phospholipids were linoleate. Under the conditions discussed, the polar head group composition, the fatty acid composition, or both together could be varied in the membrane phospholipids.

The reversible binding of the haptens 2,4-dinitrophenyllysine (DNP-lysine) and 2,4,6-trinitrophenyllysine (TNP-lysine) to either the nitrophenyl-binding myeloma protein MOPC-315 or to pooled mouse anti-DNP or anti-TNP antibodies produces large and characteristic extrinsic Cotton effects (in the circular dichroic spectra). Despite the similarities in binding characteristics of the three proteins, the circular dichroic spectra produced by the haptens bound to the active sites of these proteins were markedly different. Extrinsic Cotton effects, therefore, provide a powerful new probe of the structure of the reversible complex formed between a hapten and an antibody active site.

Nucleic acid and protein synthesis were studied in temperature-sensitive mutants defective in phospholipid synthesis. The defect is due to a single mutation in glycerol 3-phosphate acyltransferase (EC 2.3.1.15). The results show that at the restrictive temperature not only does phospholipid synthesis cease, but DNA, RNA, and protein synthesis also cease. Active transport continues, however, indicating that the cells do not become leaky or lose their energy supply. These results suggest that phospholipid synthesis is coupled to DNA, RNA, and protein synthesis.

Two homogeneous univalent hapten-protein conjugates, prepared by the covalent attachment of a single 2,4-dinitrophenyl (DNP-) or 2,4,6-trinitrophenyl (TNP-) side chain to the cysteine-SH in the active site of the enzyme papain, have been found to exhibit large Cotton effects in the wavelength region of the absorption bands of the DNP or TNP groups. This indicates that the DNP or TNP groups are noncovalently bound to some asymmetric region(s) of the papain molecule. These homogeneous papain conjugates are antigens that can elicit anti-DNP or anti-TNP antibody production in mice or rabbits. It is suggested that the noncovalent binding of a hapten to the surface of its carrier protein may profoundly affect the characteristics of the anti-hapten antibodies that are elicited. It has also been observed that the specific binding of these papain conjugates, and of the simple haptens DNP-lysine or TNP-lysine, to anti-hapten antibodies produces characteristic extrinsic Cotton effects.

The effects of temperature and of the action of a purified phospholipase C enzyme preparation on human red blood cell membranes has been investigated by chemical analyses, circular dichroism, and proton magnetic resonance measurements. The results indicate that a substantial fraction of the phospholipids and the proteins of the membranes can change structure independently of one another, suggesting a mosaic pattern for the organization of the lipids and proteins in membranes.