Paul H. Maurer

[2] Proteins and polypeptides as antigens

Publisher Summary This chapter discusses the role of proteins and polypeptides as antigens. Antibodies against enzymes can be used to detect and assay quantitatively the concentration of enzymes; to concentrate and purify the enzymes from dilute solutions and mixtures; to study the active catalytic sites, multimolecular forms, and conformational structures of the enzymes; to localize the enzymes in sectioned cells; and to study the appearance and modification of the enzymes in the course of embryonic and phylogenetic development. Concomitantly, in immunology, there has been increasing knowledge concerning many factors that can influence the multifaceted and complex sequence of events of the immune response, beginning with the introduction of an antigen into a host (immunogen) to the formation of humoral antibody. This chapter discusses the information about techniques that have become available for producing antibody. It also attempts to make an investigator aware not only of factors that might enhance antibody formation, but also of factors that might be operative in the suppression of the immune response.

Half-Lives of Homologous Serum Albumins in Several Species.

Summary The half-lives of homologous serum albumins in humans, cows. dogs, rabbits and mice have been presented. The albumin half-lives are similar to the gamma globulin half-lives for the same species and apparently are dependent upon the metabolic characteristics of the host.

Dextran, an antigen in man.

Summary It has been confirmed that native and clinical dextrans are antigenic in man. Three weeks after injection of 1 mg of dextran precipitins and cutaneous wheal and erythema sensitivity developed. The presence in human sera of antibodies to the pneumococcal polysaccharides which cross react with dextrans in other species (rabbit and horse) appears to have little to do with the reaction of humans to dextran. Antibodies produced after immunization with dextran have been shown to be specific for dextran. The persistence of antibodies to dextran has been shown.

Immunoglobulins of sheep.

Abstract Immunoelectrophoretic analysis of fractions obtained by DEAE-Sephadex ion exchange chromatography suggests that ovine immunoglobulins may comprise at least five distinct classes. In addition to the electrophoretically slow γ2 and fast γ1 immunoglobulin G, there exists another closely related immunoglobulin which may be either another immunoglobulin G or an analog of human immunoglobulin D. Immunoglobulin M and a fraction containing mainly immunoglobulin A have also been prepared. Antibody activity against dinitrophenyl-bovine serum albumin and a heteropolymer composed of glutamic acid, alanine, and tyrosine was found in the slow and fast immunoglobulin G fractions. The slow and the fast immunoglobulin G preparations were also degraded by papain. Analyses made on the recovered breakdown products suggest their close resemblance to similarly prepared fragments of immunoglobulin of man, rabbit, and other mammals.

Modified bovine serum albumin. I. Preparation and physicochemical studies of some derivatives.

Abstract The effect of nitrous acid treatment (deamination), acetylation, guanidination, and heat denaturation upon bovine serum albumin was measured by several physicochemical methods (solubility, paper electrophoresis, sedimentation, agar diffusion, viscosity, dye binding, and optical rotation). Each modification brought about significant changes in the physical properties of BSA, but the nature and extent of the effects are different in each case.

Modified bovine serum albumin. II. Immunochemical studies.

Abstract Quantitative immunochemical studies were made of the homologous and heterologous reactions of bovine serum albumin; its deaminated, acetylated, and guanidinated derivatives; and the heat-treated products of these derivatives. It has been shown that the —NH 3 + groups per se do not participate in the interaction of BSA with its antibody. It was found that heat treatment brought about greater immuno-chemical changes in BSA, than did chemical modifications. Acetylated and highly deaminated derivatives of BSA appeared to be resistant to heat, while BSA and the guanido derivative were profoundly altered upon heating.

Attempts to Produce Antibodies to a Preparation of Polyglutamic Acid.

Summary Data have been presented to show that detectable antibodies were not observed in man, rabbit or the guinea pig against a preparation of polyglutamic acid. The differences in properties between Blouts and Stahmanns PGA have been mentioned as the possible reason for differences in antigenicity of the two preparations.

Modified bovine serum albumin. III. Hydrolysis studies with trypsin, chymotrypsin and pepsin.

Abstract 1. 1. Previous work on the acetylated, guanidinated, and deaminated derivatives of BSA and their heat-denatured products was extended to a study of their behavior as substrates to the three proteolytic enzymes trypsin, chymotrypsin, and pepsin. 2. 2. Each derivative acts as a different and individual protein with its own characteristic kinetics of hydrolysis by the three enzymes. As judged by proteolysis studies, all the three chemical modifications brought about denaturation of BSA. 3. 3. The observed changes in the pH optima, Michaelis-Menten constants, and rates of proteolytic hydrolysis of the derivatives of BSA are discussed in terms of steric effects, changes in the charge distribution or altered specificity of protein resulting from the chemical modifications.

Antigenicity of Polypeptides (Poly Alpha Amino Acids). X. Studies with Polymers of D Amino Acids.

Summary It has been shown that random copolymers of D amino acids (gluala, glu ala tyr) are not antigenic in rabbits or guinea pigs. A hapten coupled to a Damino acid polymer was not immunogenic. This lack of immunogenicity has been ascribed to the inability of unnatural synthetic polymers to be degraded by known enzymes. The interaction of the polymers of D amino acids with antisera against the L forms of the same polymer was detectable only by the PCA reaction. Reasons for the non-immunogenicity of the D polymers and their interactions with antibody have been discussed.

Immunochemical studies on some acetylated proteins; acetylated rabbit serum albumin, an antigen in rabbits.

Abstract 1. 1. The effects of the acetylation reaction on rabbit serum albumin, bovine serum albumin, human serum albumin, and rabbit γ-globulin as revealed by immunochemical techniques have been investigated. 2. 2. Acetylated rabbit serum albumin is shown to be antigenic in rabbits. 3. 3. Acetylated proteins exhibit cross reactions with the antisera produced against other acetylated proteins. 4. 4. The bearing of these findings on the implication of −NH 3 + groups of the antibody in the bovine serum albumin-antibovine serum albumin interaction, and on the conditions for the antigenicity of proteins in general, is discussed.