A Human Alloantiserum Precipitates Ia-Like Molecules from Chronic Lymphocytic Leukemia Cells

Alloantigens specific for human B lymphocytes can be identified with selected antisera. These antigens have similarities to murine Ia antigens in that they are found on human B lymphocytes and are controlled by genes linked to genes controlling HLA. Chronic lymphocytic leukemia cells bearing B cell antigens were labeled with 3H leucine and the membrane components reacting with the B cell antisera isolated by immunoprecipitation. These membrane components had m.w. of 33,000 and 24,000 daltons similar to the murine Ia antigens. The results complete the homology of murine Ia and human B cell alloantigens.

A human alloantiserum precipitates Ia-like molecules from chronic lymphocytic leukemia cells

Alloantigens specific for human B lymphocytes can be identified with selected antisera. These antigens have similarities to murine Ia antigens in that they are found on human B lymphocytes and are controlled by genes linked to genes controlling HLA. Chronic lymphocytic leukemia cells bearing B cell antigens were labeled with 3H leucine and the membrane components reacting with the B cell antisera isolated by immunoprecipitation. These membrane components had m.w. of 33,000 and 24,000 daltons similar to the murine Ia antigens. The results complete the homology of murine Ia and human B cell alloantigens.

Partial chemical characterization of Ia antigens derived from murine thymocytes

Previous chemical studies attempting to demonstrate Ia antigens on mouse thymocytes have given contradictory results. We attempted to resolve the question of whether Ia antigens exist on thymocytes (defined as thymus cells that bear a T cell marker) by isolating strain C3H thymocytes free of other contaminating cells using the fluorescence-activated cell sorter, and then chemically testing the purified populations for Ia antigens. Immunoglobulin-negative thymus cells and thymus cells selected with a rabbit antiserum to mouse brain were the two populations of thymocytes labeled with [3H]leucine after sorting. Radiolabeled proteins were solubilized with the non-ionic detergent Nonidet P-40, reacted with anti-Ia antiserum, and analyzed by electrophoresis on discontinuous sodium dodecyl sulfate/polyacrylamide gels. Ia antigens were recovered from both cell populations. These antigens were synthesized by thymocytes and were found on molecules composed of two chains of molecular weight 33,000 and 25,000, respectively, similar to Ia antigens derived from spleen cells. Assuming that all thymocytes bear similar amounts of Ia antigens, we estimated that they have approximately 1/50 the amount of Ia antigens that spleen cells do.

Mutant lines of guinea pig L2C leukemia. III. The reaction of an alloantiserum detecting idiotypic determinants on a clonally derived guinea pig B cell leukemia with IgM and Ia molecules

An alloantiserum was prepared in a strain 13 guinea pig against the GH line of the strain 2 guinea pig L2C leukemia. This serum contained antibodies to both IgM and Ia molecules. After absorption with normal spleen cells from a strain 2 guinea pig, this antiserum no longer reacted with strain 2 cells, but detected idiotypes on the IgM molecules of the L2C leukemia. These idiotypes were on the same IgM molecules detected by a xenogeneic sheep anti-L2C Fab mu antiserum. As assayed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the idiotype-bearing IgM molecules were synthesized by the cell, composed of normal sized mu and light chains, appeared on the cell surface as monomeric IgM, and were the only immunoglobulin molecules present on the cell. Although the alloantiserum potentially contained antibodies to unique Ia idiotypic determinants, none were found. Furthermore, the anti-IgM idiotype antisera did not react with any Ia-like molecules.

An improved method for isolation of H-2 and Ia alloantigens with immunoprecipitation induced by protein A-bearing staphylococci

Mouse alloantigens, including the histocompatibility (H-2) and immune response linked (Ia) antigen molecules, can be readily isolated by a new precipitation technique utilizing protein A-bearing, fixed Staphylococci. The antigens are prepared by radiolabeling mouse spleen cells with 3H-leucine, solubilizing with the non-ionic detergent Non-Idet P-40, and purifying by affinity chromatography with lentil lectin coupled to Sapharose. The antigen preparations are mixed with appropriate alloantisera, and immune complexes formed in the mixture are then bound by the protein A sites on the Staphylococci. The organisms, Staphylococcus aureus, Cowan I strain (ATCC 12598), are heat inactivated and fixed, and are a stable, uniform IgG-binding reagent, especially when stored frozen. The antigen-antibody complexes are easily eluted from the organisms for electrophoretic analysis. The precipitation mediated by the organisms is more efficient, rapid, and artifact-free than the traditional "sandwich" precipitation technique involving anti-globulin reagents.

An Improved Method for Isolation of H-2 and Ia Alloantigens with Immunoprecipitation Induced by Protein A-Bearing Staphylococci

Mouse alloantigens, including the histocompatibility (H-2) and immune response linked (Ia) antigen molecules, can be readily isolated by a new precipitation technique utilizing protein A-bearing, fixed Staphylococci. The antigens are prepared by radiolabeling mouse spleen cells with 3H-leucine, solubilizing with the non-ionic detergent Non-Idet P-40, and purifying by affinity chromatography with lentil lectin coupled to Sapharose. The antigen preparations are mixed with appropriate alloantisera, and immune complexes formed in the mixture are then bound by the protein A sites on the Staphylococci. The organisms, Staphylococcus aureus, Cowan I strain (ATCC 12598), are heat inactivated and fixed, and are a stable, uniform IgG-binding reagent, especially when stored frozen. The antigen-antibody complexes are easily eluted from the organisms for electrophoretic analysis. The precipitation mediated by the organisms is more efficient, rapid, and artifact-free than the traditional “sandwich” precipitation technique involving anti-globulin reagents.

Studies of Ia antigens on murine peritoneal macrophages

Murine peritoneal cells, both induced and noninduced, were examined for Ia antigens by a variety of techniques. Complement-mediated cytotoxicity and indirect immunofluorescence, analyzed by both visual microscopy and the fluorescence-activated cell sorter, detected Ia antigens on the surface of an average of 8% to 15% of cells with the morphologic and functional characteristics of macrophages. Internal radioisotope labeling studies showed that these antigens were actually synthesized by the macrophages. The antigens were borne on molecules which consisted of two coponents with apparent molecular weights of roughly 33,000 and 25,000 daltons. At least some of these molecules existed as a two-chain structure of 58,000 daltons linked by disulfide bonds. Although macrophage Ia antigens appeared to be structurally similar to the Ia antigens found on spleen cells, the radioisotope labeling studies indicated that the quantity of labeled Ia-bearing molecules isolated from peritoneal macrophages was at most 1/15 that found for B lymphocytes. In addition, anti-Ia antisera failed to inhibit the binding of heat-aggregated immunoglobulin to the Fc receptor of macrophage populations, similar to the low levels of Ia antigens found in T-lymphocyte populations. These studies suggest that Ia antigens exist only a subpopulation of peritoneal macrophages. Alternatively, all cells in the population might bear small amounts of Ia antigens with only a fraction having sufficient numbers of molecules to be detected by the assay systems used.

Structural characteristics of the alloantigens determined by the major histocompatibility complex of the guinea pig

The GPLA B and Ia (I region-associated) antigens are the products of genes found in the guinea pig major histocompatibility complex. Because of their importance in immune response phenomena, a structural study of these antigens was undertaken. [3H]leucine and [3H]fucose were internally incorporated into guinea pig lymph node cells. The GPLA B and Ia antigens were solubilized by the nonionic detergent Nonidet P-40, purified by affinity chromatography using an adsorbent column of lentil lectin, isolated by immunoprecipitation, and examined by discontinuous polyacrylamide-sodium dodecyl sulfate gel electrophoresis. The GPLA antigens B.1, B.2, B.3, and B.4, were shown to be glycoproteins of mol wt 40,000 daltons and to be noncovalently associated with a 12,000 dalton protein. The molecules bearing B.2 and B.3 in a B.2/B.3 heterozygote are shown to be separable, suggesting the antigenic determinant is a primary gene product. In addition, a new GPLA determinant, S, which resembles the B antigen in that it is found on a molecule of approximately 40,000 daltons, was studied. In a B.2/B.3 S+ animal the molecule bearing antigen S was shown to be independent of those bearing B.2 and B.3, providing evidence that the genes determining B and S are at separate loci. The Ia-bearing molecules identified by anti-Ia.2,4 are glycoproteins of mol wt 58,000 daltons which are composed of two subunits of 33,000 and 25,000 daltons, respectively, linked by disulfide bonds. The Ia-bearing molecules are independent of GPLA-bearing molecules, indicating different loci determining these antigens. By all criteria, the guinea pig GPLA B antigens appear homologous to the murine H-2D and H-2K antigens, while the guinea pig Ia antigens appear homologous to the Ia antigens of the mouse.

The major histocompatibility complex of the guinea pig. I. Serologic and genetic studies

Serologic and genetic studies of the antigens which comprise the guinea pig MHC have demonstrated three distinct but linked genetic regions. Antisera to the B region were raised by cross-immunization of random-bred animals; this region controls antigens B.1, B.2, B.3, and B.4 which behave as alleles at a single locus and which resemble the products of the murine D or K region genes in their tissue distribution and molecular characteristics. Cross-immunization of inbred strain 2 and strain 13 animals, both of which bear the B.1 antigen, leads to sera which identify antigens which resemble the products of the I region of the murine MHC. Specific absorption experiments have demonstrated four distinct I region antigens. In addition to the B and I regions, inbred strain 2, strain 13, and some outbred animals bear an antigen (S.1) which is the product of a third genetic region and which also resembles the murine D or K region gene products in molecular size. The results of these studies should facilitate the use of the guinea pig as an experimental model for studies of genetic control of the immune response and the function of the histocompatibility-linked Ir genes.

The molecular basis of codominant expression of the histocompatibility-2 genetic region

H-2 alloantigens in an intact, undegraded form can be solubilized by the nonionic detergent NP-40 and isolated by indirect immunoprecipitation and electrophoresis in sodium dodecyl sulfate on polyacrylamide gels. With the use of an immunological precipitation method, the question about the number of cellular H-2 gene products in heterozygous cells has been partially resolved. At least four separable gene products were detected in cells heterozygous at the H-2 genetic region-one for each of the H-2D genes of the two parental haplotypes, and one for each of the H-2K genes of the two parental haplotypes. This is in contrast to the two H-2 gene products reported previously for cells homozygous at the H-2 region. The findings establish that the two parental H-2 haplotypes on homologous chromosomes in heterozygous cells are ultimately expressed as different glycoprotein molecules.

The Distribution of Alloantigenic Specificities of Native H-2 Products

Studies on radiolabeled, detergent-solubilized H-2 alloantigens of two different genotypes with indirect immunoprecipitation show that at least two different antigen molecules can be isolated from cells of each genotype. These H-2 alloantigen molecules may bear the antigenic sites for one, two or more specificities. The findings are consistent with recent views that the H-2 genetic region includes two genes, each of which directs the synthesis of a different H-2 alloantigen molecule.

Isolation of H-2 Alloantigens Solubilized by the Detergent NP-40

Murine tumor cells of two different H-2 genotypes (H-2b and H-2d) were radiolabeled in suspension culture with 3H-fucose, and intact, labeled cells were extracted with the non-ionic detergent NP-40. Solubilized native molecules bearing H-2 alloantigenic activity were isolated from other cell constituents by indirect immuno-precipitation. SDS-polyacrylamide gel electrophoretic analysis of specific precipitates of 3H-fucose-labeled H-2 alloantigens resulted in radiolabel patterns, that gave single peaks for each mouse strain examined. These peaks were proved to be H-2 alloantigens by competition experiments in which the alloantiserum used in the indirect precipitation was pretreated with a papain-solubilized, unlabeled, highly purified splenic H-2 alloantigen preparation of the same H-2 type. The efficiency of the NP-40 solubilization procedure was estimated to be nearly 100%.