THE EXPRESSION OF HISTOCOMPATIBILITY ANTIGENS ON CELLULAR AND SUBCELLULAR MEMBRANES

Genetic regulation of the expression of H-2-K.5 antigen of erythroid cells by H-2K end

Difference in the amounts of H-2K.5 antigens present on erythrocytes was observed, using quantitative absorption method, among several B 10 congenic strains. However, no such variation was seen on the lymphocytes and lung cells. The variability in the amount of this antigen on the erythrocyte surface was primarily dependent on the haplotype of the H-2K end in the B 10 recombinant strains examined. This suggests that the regulator of H-2 expression on erythrocytes is in this region. Further genetic analysis confirmed that this regulation functions in the cis-position. Finally, the H-2K.5 antigenic activity was expressed on the reticulocytes of all strains tested, but appeared lower in the type 2 group indicating that the regulation begins early in erythropoietic differentiation and eventually results in a complete loss of detectable activity.

Differences in the expression of histocompatibility antigens on mouse lymphocytes and tumor cells: immunochemical studies

Immunochemical studies have shown that labeled, detergent-solubilized extracts of SL2 (H-2d) lymphoma cells contain components reactive with several anti-H-2 alloantisera of restricted specificity. Anti-H-2k and anti-H-2ja as well as anti-H-2d sera precipitated labeled polypeptides of a molecular weight similar to that of H-2 heavy chains. In addition, all antisera tested precipitated a component of 70000 daltons molecular weight, which is antigenically related to gp 69/71 of Friend murine leukemia virus. Reactions with antisera directed against haplotypes other than H-2d could be blocked by addition of unlabeled, detergent-solubilized extracts of H-2d lymphocytes, or by H-2 antigens against which the antiserum was directed. Sequential immunoprecipitations initially using antisera against the K, D, or L region gene products to remove individual known H-2d antigens have made possible the identification of some molecules responsible for these reactions. The results show that antisera against haplotypes other than H-2d which react with SL2 cells, cross-react with normal H-2d antigens. Quantitative absortion of these antisera with intact or solubilized cells has shown that lymphocytes and tumor cells differ in their expression of some H-2 determinants. The antibodies bind only weakly to intact H-2d lymphocytes, but strongly to the corresponding detergent-solubilized antigens. These results do not, therefore, support the derepression hypothesis put forward earlier.

T-cell-deficient mice produce more antihapten antibodies against syngeneic than against allogeneic erythrocyte conjugates

T-cell-deficient mice, either anti-thymocyte serum treated or nude mice, were immunized with hapten (4-hydroxy-3,5-dinitrophenyl acetic acid, NNP) conjugates of syngeneic, allogeneic, or xenogeneic erythrocytes. Immunization with syngeneic conjugates led to a stronger anti-NNP response than immunization with allogeneic or xenogeneic conjugates. A study of congenic mouse strains suggested that a prerequisite for this effect was that immunogenic erythrocytes and responding animals shared H-2-controlled characteristics. F1 hybrid erythrocyte conjugates injected into F1 hybrid mice behaved like other syngeneic erythrocytes. The same erythrocyte conjugates injected into either parental strain induced a weak response indistinguishable from the response to allogeneic erythrocyte conjugates. Parental erythrocyte conjugates injected into F1 mice induced an anti-NNP response that was significantly lower than the response to F1 erythrocyte conjugates but significantly higher than the response to allogeneic conjugates. The response of normal mice to syngeneic erythrocytes was weaker than the response of T-cell-deficient mice, which could have been caused by suppressor T cells. Their response to allogeneic conjugates was higher than the response of T-cell-deficient mice and the response to xenogeneic conjugates higher still. This was probably due to allo- or xenoreactive helper cells.

The Ia antigens

The Ia antigens constitute a polymorphic series of cell surface determinants. At present, their definition is mainly a genetic one, and thus any cell surface antigen which can be demonstrated to be encoded by a gene in the Ir region of the H-2 complex may be classified as an Ia antigen. There are presently three subregions of the I region defined on the basis of available recombinant haplotypes, and designated at I-A, I-B, AND I-C. Mapping of individual Ia specificities indicates that numerous specificities are determined by genes in the I-A subregion, several in the I-C subregion, and few, if any, in the I-B subregion. This may be a reflection of the state of the art, however, rather than an accurate assessment of the extent of polymorphism. The Ia antigens appear to be expressed preferentially on the B-cell subpopulation of lymphoid cells. However, with the use of sensitive techniques they have also been demonstrated on some T cells, on macrophages, on sperm cells, and on epidermal cells. The Ia antigens have also been demonstrated on several T-cell factors which appear to be involved in the immune response. Whether or not all of the Ia antigens thus localized are identical or represent overlapping specificities within the same sera remains in many cases to be determined. There are presently three ways of defining Ia specificities serologically: (1) by direct immunization between strains differing only in the I region; (2) by detection of shared Ia determinants using polyspecific sera which contain H-2K region and H-2D region antibodies but which are nevertheless specific only for Ia antigens when tested on target cells of other strains; and (3) by selective absorption of H-2K region and H-2D region antibodies from an H-2 antiserum by cells bearing these antigens but lacking (or relatively lacking Ia antigens. All three of these methods produce anti-Ia reagents of reasonable titer for use in both serological and functional experimentation. The definition of the specificity as an Ia specificity in each case requires the availability of appropriate recombinant strains to map the specificity to the Iregion. In addition, there are several correlative criteria which have been developed in order to detect Ia activity in alloantisera in the absence of the availability of appropriate recombinants for mapping of the specificity. These include the tissue distribution of the Ia antigens (namely, their predominant expression on the B-cell subpopulation), their characteristics molecular size, their association on the B-cell surface with the Fc receptor, and their lack of association with other products of the major histocompatibility complex as distinguished either chemically or by cocapping studies. These correlative criteria make it possible to distinguish probable anti-Ia reactivity in a variety of serological reactions, but the results must still be interpreted with caution until appropriate recombinants have been obtained which can map the specificities to the I region...

Preparation of aminoazo dye induced rat hepatoma membrane fractions retaining tumour specific antigen

Membrane fractions were isolated from homogenates of an aminoazo dye induced rat hepatoma (hepatoma D23) by sucrose density gradient centrifugation in zonal rotors. The membrane fractions retained tumour specific antigenic determinants and exhibited an increased antigenic activity over other subcellular membrane fractions, as defined by their capacity to quantitatively neutralize the membrane immunofluorescence staining of viable hepatoma D23 cells by antibody in tumour immune serum. In contrast, no antigenic activity was found to be associated with purified hepatoma D23 nuclei or nuclear membranes as evaluated by the in vitro antigen assay.The two methods described for the isolation of hepatoma D23 membranes have been developed for the large scale fractionation of tumour homogenates in order that further studies upon the nature and immunogenicity of membrane associated tumour specific antigens may be resolved using defined membrane preparations of increased antigenic activity.

The influence of DL-A compatibility on the survival of hepatic allografts in unmodified mongrel dogs

Heterotopic hepatic transplantation was performed in 26 pairs of littermate and non-littermate mongrel dogs selected by serological criteria of DL-A compatibility. No immunosuppression was given. In non-littermates, 11 recipients of DL-A incompatible allografts survived 10-22 days (mean 13.4 days). Mean serum bilirubin rose by the 6th day. Three recipients of DL-A compatible allografts survived 13, 41, and 60 days, (mean 38 days). Mean serum bilirubin rose by the 8th day. In littermates, 5 recipients of DL-A incompatible allografts survived 7-12 days (mean 10.2 days) and mean serum bilirubin rose by the 6th day. Four recipients of DL-A compatible allografts from phenotypically DL-A non-identical donors survived 58, 82, 90 and 128 days (mean 89.5 days). Mean serum bilirubin rose by the 29th day. In contrast, 3 recipients of DL-A phenotypically identical allografts survived 171, 536 and over 636 days respectively, with normal mean serum bilirubin levels. The results confirm the role of the DL-A system in hepatic transplantation in mongrel dogs, and suggest that this dog population may constitute a suitable experimental model parallelling the current situation with regard to HL-A compatibility testing in outbred human subjects. The relatively long survival of DL-A compatible heterotopic hepatic allografts, compared with similar transplants of skin, kidney and heart, also suggests a need for studies of possible alteration in parameters of humoral and cellular reactivity in these recipients.

Characterization of rat liver subcellular membranes. Demonstration of membrane-specific autoantigens

The induction of acute hepatocellular necrosis in rats resulted in the production of complement fixing, IgM autoantibodies directed toward inner and outer mitochondrial membranes, microsomal membrane, lysosomal membrane, nuclear membrane, cytosol, but not to plasma membrane. Utilizing selective absorption procedures it was demonstrated that each subcellular membrane fraction possessed unique autoantigenic activity with little or no cross-reactivity between the various membrane fractions. It is proposed that the development of membrane-specific autoantibodies may provide an immunological marker useful in the differential characterization of various subcellular membranes.

Electrophoretic mobility and agglutinability of red blood cells: a "new" polymorphism in mice

A quantitative method has been developed to determine agglutinability of mouse red blood cells. Tests with different inbred strains of mice revealed only two phenotypes. The same inbred strains were tested with the cytopherometer to determine the electrophoretic mobility of the corresponding red cells. Again, two phenotypes were uncovered, and faster mobility was found in the red cells that had higher agglutinability. The genetic control of this character is autosomal and codominant, and segregates independently of H-2 and coat color.

Synthesis, intracellular distribution, and secretion of immunoglobulin and H-2 antigen in muring splenocytes

A/J spleen cells were labeled with [(3)H]leucine and at intervals thereafter were homogenized and separated into microsomes and cell sap. Ig and H-2 antigens were assayed in the cell fractions and cell supernatants using immunoprecipitation. In addition, cells labeled by enzymatic radioiodination were incubated to determine the rates of release of Ig and H-2 antigens from the surface. The results indicate that the majority of Ig and H-2 antigens remain membrane bound throughout their intracellular life. In contrast to Ig, H-2 antigens are neither secreted nor shed from the cell surface. It is suggested that Ig is a peripheral protein of the cell membrane, whereas H-2 antigens are integral ones. The release of Ig on a fragment of plasma membrane could occur at fixed cell surface areas that contain no H-2 antigens or from which they have migrated before release.

H-2 antigens on nuclear membranes

Nuclei and nuclear membranes were examined for the presence of H-2 histocompatibility antigens in the mouse. These were detected on thymus as well as on liver preparations by means of ⁵¹Cr-cytotoxocity inhibition and complement fixation tests, absorption experiments and by the immunogenic properties of these preparations.

Induction of immunological tolerance to soluble histocompatibility-2 antigens of mice

Immunological tolerance to a soluble, partially purified fraction of histocompatibility (H)-2(a) antigen was induced in B10.D2 strain mice. The fraction used was obtained after chromatography on a Sephadex G-150 column. Tolerance of humoral-antibody formation (cytotoxins and hemagglutinins) was observed in mice injected with soluble antigen since birth, but cell-mediated immunity, as measured by skin graft survival, remained intact. Tolerance was shown to be specific for H-2(a) antigens, since treated mice produced a regular humoral-antibody response to H-2(b) antigens. These findings, along with previous observations of the immunogenic and enhancing properties of our partially purified fraction, suggest that the solubilized antigen contains all the major determinants of H-2(a) antigens expressed on lymphoid-cell surfaces.

Xenogeneic recognition of tumour spcific plasma membrane antigens derived from mouse lymphoma cells

Rabbit antisera were prepared to two mouse ascitic lymphomas, one of them being highly immunogenic, the other one weakly immunogenic in syngeneic hosts. A comparison was made between antisera raised with intact cells and antisera raised with cell-free fractions composed of purified large plasma membranes. The antisera were tested in vitro for their lytic capacity by the ⁵¹Cr-release technique, and in vivo for their capacity to protect syngeneic mice against a tumour challenge. The antisera were used unabsorbed, absorbed with syngeneic mouse tissue, and also after passage through syngeneic animals. The antisera with the highest specificity for the respective tumour in mice were those raised by plasma membranes derived from the strongly immunogenic tumour. Lysis in the ⁵¹Cr test corresponded roughly with these findings. Xenogeneic recognition of tumour distinct antigens as well as the therapeutic value of xenogeneic antisera against established lymphomas growing in the ascitic form are discussed.

Serological and immunogenic activity of soluble mouse transplantation antigens controlled by the H-2 locus

The solubilization and partial purification of mouse transplantation antigens were monitored by (1) an in vitro assay for alloantigenic specificities and (2) an in vivo assay for transplantation antigens controlled by the H-2 histocompatibility locus. Antigens from A/J mice were solubilized by papain and fractionated on a Sephadex G-150 column. The eluate showed a 280 nm absorbance peak (F(1)) in the excluded volume and two peaks (F(2) and F(3)) in the included volume. H-2 specificities 1, 3, 4, 5, 11, 23, and 28 were confined to a single peak in the F(2) fraction. Fractions F(1), F(2), and F(3), were tested for their ability to accelerate skin graft rejection in noncoisogenic strains which differ at both H-2 and non-H-2 loci, and coisogenic strains which differ only at the H-2 locus. All fractions produced significant acceleration of graft rejection in the noncoisogenic strains, but only fraction F(2) produced significant acceleration in the coisogenic strains. These findings indicate that H-2 transplantation antigens detected by our in vivo assay, and H-2 alloantigenic specificities detected by our in vitro assay are solubilized by papain and are eluted in the same peak during Sephadex fractionation.

Human renal transplants. 3. Immunopathologic studies

Tissues obtained from 34 human renal allografts by biopsy, 1 to 31 months after transplantation, were studied by histologic, immunofluorescence, and immunoferritin techniques. Our purpose was to gain more precise information concerning the localization of immunoglobulins and complement in glomeruli and to describe the associated tubular and vascular changes. Localization of fluorescein-labeled antibodies (Fl-Abs) to IgG, IgM, β 1C, and C′1q was seen in glomeruli from 25 allografts and showed the following distribution of patterns: (a) diffuse linear, four; (b) diffuse granular, four; (c) focal linear, six; (d) focal granular, six; and (e) indeterminate, five. Ferritin-conjugated antibodies (Fer-Abs) localized in 21 allografts. Electron microscopic findings correlated with the foregoing immunofluorescence patterns. (a) Fer-Abs were bound on the endothelial side of the glomerular basement membrane and in the subendothelial space. (b) Fer-Abs were bound in subendothelial and subepithelial deposits similar to those seen in experimental acute or chronic serum sickness. (c and d) Fer-Abs were seen in the subendothelial space and mesangial matrix. Deposits were present in these areas and some bound Fer-Abs. The two groups were not readily separable on the basis of immunopathologic data. (e) Fer-Abs were mostly seen in the mesangial area. Nine allografts displaying little or no binding of Fl-Abs failed to bind Fer-Abs. Small amounts of fibrinogen were found in only six allografts, three of which showed diffuse granular fluorescence. In 12 allografts either Fl-Abs or Fer-Abs or both were bound in walls of blood vessels. The position of these reactants was in foreign deposits and in basement membranes of arteries and veins.

The immunopathologic findings seem to support best the hypothesis that damage to allografts is associated with deposition, in glomerular and vascular structures, of circulating antigen-antibody complexes which might contain, in part, transplantation antigens.

Mouse histocompatibility isoantigens derived from normal and from tumour cells

A simple method is described for preparing mouse histocompatibility antigens of high specific activity. Material is eluted from cells in hypotonic salt without allowing cytolysis; a suitable degree of hypotonicity depends on the cell type. Specificities determined by H-2 and some non-H-2 alleles have been measured by inhibition of release of radioactivity from labelled target cells incubated in isoantiserum and complement. Certain tumour cells and the antigens isolated from them have aberrant histocompatibility antigen composition.