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Human erythrocytes contain a membrane protein, MACIF, which inhibits the formation of a membrane attack complex (MAC) of complement. We have cloned and sequenced the complementary DNA of MACIF messenger RNA. The amino acid sequence predicted from its nucleotide sequence consists of 128 amino acids. The amino-terminal 25 residues may correspond to a signal peptide. The carboxy-terminal sequence confirmed that MACIF is a glycosylphosphatidylinositol (GPI)-anchored protein. The amino acid sequence of MACIF was partially determined by established techniques for protein chemistry and the resultant sequence was consistent with that predicted from the nucleotide sequence. The results of sequence analyses also suggested that asparagine at the 18th position was N-glycosylated. When mRNA obtained from the MACIF cDNA clone with SP6 RNA polymerase was microinjected into Xenopus oocytes, the oocytes synthesized a product which exhibited MACIF activity and reacted with anti-MACIF antibody. Comparison of the predicted sequence revealed significant homology with mouse Ly-6 antigens.

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Dielectric relaxation and Brillouin scattering are jointly used in studying molecular relaxation in poly(propylene oxide) (PPO) and its solutions in methylcyclohexane. The dielectric method was applied to the more concentrated (100%, 80%, 60%, by volume) solutions over a wide temperature and frequency range (30 Hz to 8 GHz) in order that the variation in activation energy characteristic of a glass‐forming substance could be delineated. The present work extends previous work on the undiluted polymer to higher frequencies so that range of 12 decades in the dielectric loss maximum fmax as a function of temperature is now available. The “Antoine” equation is found to represent the behavior of log fmax, of the bulk concentrated solutions very well. The more dilute (40%, 20%) solutions were studied only in the high‐frequency (GHz) region since phase separation occurred at low temperatures. Both the temperature and dilution effects were interpreted in terms of free‐volume theory. Brillouin scattering spectra were obtained at several scattering angles and a wide range of temperatures. A maximum in the curve of hypersonic attenuation versus temperature was observed in each polymer solution. The attenuation maximum shifts toward lower temperature upon dilution, in agreement with the dielectric relaxation result. The Brillouin scattering follows different activation parameters and evidences a more rapid process than does the dielectric relaxation. It is speculated that it monitors a secondary or subglass relaxation, due perhaps, to damped torsional oscillations.

A humanized monoclonal IgG1 antibody, designated hC4G1, recognizes the fibrinogen receptor glycoprotein (GP)IIb/IIIa on platelets and inhibits platelet aggregation. When the F(ab')2 fragment of hC4G1 (F(ab')2 hC4G1) was administered to cynomolgus monkeys, all the monkeys showed inhibition of platelet aggregation ex vivo. Unexpectedly, a significant decrease in platelet count was observed in 5 of 18 monkeys. Antibodies against F(ab')2 hC4G1 were detected in the plasma of these monkeys by ELISA. Antibody activity in the plasma of these monkeys was significantly correlated with the intensity of platelet decrease (r = 0.84). The natural monkey antibodies to F(ab')2 hC4G1 were directed against the C-terminal region of F(ab')2 fragment common to all human and humanized IgG antibodies. Natural homo-reactive antibodies were also detected in human plasma from 15 of 40 healthy volunteers. Specificity was closely similar to that of the monkey antibodies. Affinity-purified human homoreactive antibodies enhanced phagocytosis of platelets treated with the F(ab')2 hC4G1. Monkey plasma with high homo-reactive antibody activity was confirmed to decrease platelet count when administered together with F(ab')2 hC4G1 to a monkey with low antibody activity. These results suggest that F(ab')2 of humanized and human antibodies causes elimination of the corresponding antigens from the circulation by homo-reactive antibodies.