Genetic control and carrier and suppressor effects in the antibody response of mice to procollagen

Immunochemical properties of the aminopropeptide of procollagen type III

The precursor-specific aminopropeptide of bovine type III procollagen is a strong immunogen in rabbits, guinea pigs and mice and induces antibodies which do not cross-react with type I procollagen. The antibody response is regulated by immune response genes associated with the major histocompatibility complex. Major antigenic determinants were found in the compact, non-collagenous domain (fragment Col 1) located at the N terminus of the aminopropeptide and were destroyed by reduction of disulfide bonds. Minor antigenic determinants independent of disulfide bonds also exist in fragment Col 1 and could be localized on a distinct tryptic peptide. Fragment Col 1 showed a lower affinity for antibody when compared with the intact aminopropeptide which causes a non-parallel shift in radioimmuno-inhibition profiles. Monovalent antibody fragments showed an average tenfold reduction in affinity constant and failed to distinguish between aminopropeptide and fragment Col 1. This indicates that the stronger binding of bivalent antibody by the triple-stranded aminopropeptide is due to multiple interactions with both antibody binding sites which are lost for a single-stranded antigen (Col 1) or with monovalent antibody fragments.

A monoclonal antibody specific for the amino terminal cleavage site of procollagen type I

A monoclonal mouse IgG1 antibody was produced against the aminopropeptide of dermatosparactic sheep procollagen type I by using the hybridoma technique. Radioimmunoassays demonstrated an apparent affinity constant of 10(8) l X mol-1. The antibody reacted with a 19-amino-acid-long sequence spanning the procollagen N-proteinase cleavage site with stronger binding to structures contributed by the aminopropeptide. The antibody showed strong cross-reactions with similar antigens of bovine, human or chick origin but failed to react with the aminopropeptide of procollagen type III. Incubation of chick or sheep procollagen type I with stoichiometric amounts of antibody blocked the release from procollagen molecules of the aminopropeptide by procollagen N-proteinase. Thus, this antibody seems useful for studying various biological problems encountered in the conversion of procollagen.

Genetic control of the immune response to haemoglobin. II. Studies using purified alpha-chain and beta-chain as immunogens

Mice of independent haplotypes and several recombinant inbred strains were immunized with highly purified preparations of either the alpha-chain or beta-chain subunit of human adult haemoglobin. Cells from the sensitized lymph nodes were challenged in vitro with the appropriate subunit (or in some cases both chains) and cell proliferation assessed by 3H-thymidine incorporation. Mice of the H-2b and H-2d haplotypes were high responders to alpha-chain while mice of the H-2f, H-2j, H-2k, H-2r, H-2s, H-2u, and H-2v haplotype were low responders. the low responsivenesss of B10.A(4R) and B 10.MBR and high responsiveness of B10 indicated that the Ir gene(s) determining responsiveness to the alpha-chain subunit resides in the I-A subregion of the mouse major histocompatibility complex. Mice of the H-2d, H-2f, and H-2s haplotypes were high responders and H-2b, H-2j, H-2a, and H-2u haplotype mice were low responders to beta-chain. H-2k, H-2p, H-2r, and H-2v haplotype mice were intermediate responders to beta-chain. The low responsiveness of B10.S(8R) and B10.TL and the high responsivenes of B10.S(9R) mapped the Ir gene(s) to beta-chain to the I-A subregion. Data collected from challenging high responder cells with both subunit indicated that alpha-chain and beta-chain do not crossreact. These results are discussed in reference to earlier observations suggesting that the low responsiveness of some strains of mice to priming and challenging using the intact haemoglobin molecule might be due to a negative regulatory influence mediated by one of the subunits. In the absence of this influence these mice would respond normally.

The immune response to human type III and type V (AB2) collagen: antigenic determinants and genetic control in mice

The genetic influences on the specific IgG antibody response to helical antigenic determinants of native soluble type III and V (AB2) human collagen have been studied in mice. H-2-linked Ir genes have been detected for each of these collagens, as have background effects. The alleles controlling high antibody responses can be distinguished from those previously described for bovine collagen type I and type I propeptide. Apparent two-gene complementation in the response to type V (AB2) may indicate that this antigen will be a useful probe in further studies of the complex nature of antigen presentation for T cell recognition. The present studies may facilitate the production of specific, high-affinity monoclonal antibodies for the human collagens which, in turn, will facilitate the study of connective tissue biology and pathology.

Localization of antigenic activity and immunogenic capacity in different conformational domains of procollagen peptide

The antibody response to the amino-terminal CNBr peptide of sheep procollagen which consists of a globular and a collagenous segment, was studied in inbred strains of mice. The determinants reacting with antibody could be localized in the globular domain and were lost by reduction of disulfide bridges. The ability to induce an antibody response required the collagen-like sequences and was independent of the triple-helical conformation of this segment. The data were interpreted as indicating a different conformation dependence of hapten and carrier determinants.