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Biomedical subjects

L P Einstein

Publications and source records attributed to L P Einstein.

8 recordsLinked to original sources
PubMed1982

Complement proteins C2, C4 and factor B. Effect of glycosylation on their secretion and catabolism.

Tunicamycin, an inhibitor of N-acetylglucosaminylpyrophosphopolyisoprenol-dependent glycosylation, was used to study the effect of glycosylation on the synthesis, post-translational modification, secretion and function of the complement proteins that are associated with the major histocompatibility complex in humans, mice and guinea pigs. Tunicamycin blocked glycosylation of pro-C4, C2 and factor B and inhibited secretion of the corresponding native complement proteins synthesized by guinea-pig peritoneal macrophages in tissue culture. In addition, underglycosylated pro-C4 was more rapidly catabolized intracellularly than the corresponding fully glycosylated pro-complement protein. C4 protein secreted by cells incubated with tunicamycin had approximately the same specific biological activity as the protein obtained from control culture media, suggesting that carbohydrate is not required for its activity in immune haemolysis. Direct studies of carbohydrate incorporation and the tunicamycin effect suggested an unequal distribution of sugar among the C4 subunits, with maximal incorporation of carbohydrate into alpha-, and less into the beta-chain of the native protein.

Animals↗
PubMed1982

Biosynthesis of a structurally abnormal C2 complement protein by macrophages from C2-deficient guinea pigs.

In order to characterize a genetic deficiency of C2 in guinea pigs, production of C2 by peritoneal macrophage cultures derived from four normal, four heterozygous deficient, and four homozygous deficient animals was measured functionally and immunochemically after metabolic labeling with 35S-methionine. Macrophage monolayers from homozygous deficient animals failed to secrete hemolytically detectable C2 up to 74 hr in culture. A single cell hemolytic plaque assay also failed to demonstrate any functional C2 production by cells from homozygous deficient animals. No C2 protein was detected in media from three of the four homozygous deficient animals, but in one, apparent C2 fragments were present. In contrast, intracellular C2 protein was identified in all four homozygous deficient cell cultures. Its mobility on SDS-PAGE was slightly faster than normal. Much less abnormal intracellular C2 protein was recovered from homozygous deficient macrophage monolayers than intracellular C2 protein from normal macrophage monolayers. Monolayers from heterozygous animals produced functional and immunochemical C2 at approximately 30% of the normal rate. Normal rates of biosynthesis and secretion of two other MHC-linked class III antigens, C4 and factor B, were detected in macrophage cultures from homozygous and heterozygous deficient animals. These data suggest that a specific defect, i.e. a structural abnormality in C2 protein, underlies C2 deficiency in guinea pigs.

Animals↗
PubMed1977

Biosynthesis of the third component of complement (C3) in vitro by monocytes from both normal and homozygous C3-deficient humans.

Human monocytes synthesized the third component of complement (C3) up to 5 wk in vitro. Evidence for net C3 synthesis was based on (a) incorporation of 14C-labeled amino acids into C3 protein, (b) indentity of the allotype of C3 produced in vitro with that of the doner's serum C3, even in the presence of carrier C3 protein of a different allotype; (c) correspondence of electrophoretic mobility, size, and subunit structure of C3 protein produced in vitro with serum C3; (d) inhibition of C3 production with cycloheximide. Monocytes from two unrelated C3-deficient patients were studied under conditions that supported C3 synthesis by normal monocytes. Serum from each of the patients contained less than 1% of the normal C3 concentration, buth their monocytes produced C3 at approximately equal to 25% of the normal rate when studied after 2 wk in vitro. The C3 produced in vitro by monocytes from one of the patients had the molecular weight of normal serum C3 and dissociated appropriately under reducing conditions. Monocytes from C3-deficient patients could not be distinguished from normals on the basis of morphology, rosetting with C3-coated erythrocytes, or rates of C2, and total protein synthesis.

Blood Proteins↗
PubMed1976

Synthesis of the second component of complement by long-term primary cultures of human monocytes.

A method has been developed for preparation of confluent monolayers of human monocytes from small volumes of blood and for maintenance of these pure monocyte cultures for up to 16 wk in vitro. These cells phagocytosed 5.7 mum diameter latex beads, rosetted with erythrocytes coated with IgG or with C3, killed Listeria monocytogenes, and synthesized both lysozyme and the second component of complement. Lysozyme was secreted at a rate of approximately 50,000 mol/min per cell for at least 12 wk in cultures. The maximal rate of C2 synthesis and secretion was considerably less; i.e., approximately 30 mol/min per cell between the 2nd and 12th wk in culture. Monocytes produced little C2 during the first 6 days in culture after which a marked increase in the rate of C2 production was noted. This increase was coincident with morphologic evidence of monocyte maturation.

Bacteriolysis↗