THE RELATIONSHIP BETWEEN HEMAGGLUTINOGENS AND HISTOCOMPATIBILITY ANTIGENS IN THE MOUSE*

Antibody response to homografts. VIII. Relation of mouse hemagglutinins and cytotoxins

Antigenic differences between certain inbred strains of mice which could not be revealed by hemagglutination techniques were readily disclosed by lymphocyte cytotoxicity. With an improved cytotoxicity test lymphotoxic titers were as high as 1:512 with non-hemagglutinating A anti CBA antisera. In other mouse strain combinations, a close parallel of both types of antibody activity was obtained. Though both activities were absorbed from antisera proportionally by erythrocytes and lymph node cells, 100 to 1000 times as many erythrocytes as lymphocytes were necessary to produce an equivalent reduction in antibody activity. These findings suggest that erythrocytes may possess only subthreshold quantities of certain antigens which are present in readily detectable levels on lymphocytes. Lymphocyte cytotoxicity therefore may assay a wider range of allogenic antigens than hemagglutination.

THE EXPRESSION OF HISTOCOMPATIBILITY ANTIGENS ON CELLULAR AND SUBCELLULAR MEMBRANES

The mouse isoantigens determined at the major histocompatibility locus known as H-2 have been found to be closely associated with the cellular surface membranes, with the membranes of the endoplasmic reticulum, and probably with those of the lysosomes as well. Mitochondrial membranes, on the other hand, show little or no H-2 antigen activity. Membrane material prepared from certain tissues, including brain and muscle, have no detectable H-2 antigenic activity. Evidence is presented which indicates that all of the H-2 antigens of the genome are expressed as a unit, supporting the hypothesis that the complex H-2 genetic locus consists of a single cistron. It is postulated that these histocompatibility antigens form some structural or functional unit in the membranes of cells.

Immunogenicity of the mutated H-2Kbm1 antigen(s). Test of thyroid graft rejection between B6.C-H-2bm1 and C57BL/6 mice following reciprocal immunization with normal versus malignant cells

The immunogenic properties of one (or few) selected antigen(s) encoded by the mouse major histocompatibility complex was studied using the C57BL/6(B6) mouse strain and its descendant B6.C-H-2bm1(bm1) mutant. These strains differ in a point mutation in the H-2K region. We compared the immunogenic and antigenic expression of the mutated antigen on different bm1 tissues by testing the vulnerability of these tissues to graft rejection response in B6 recipients. Previous results demonstrated that B6 and bm1 mice do not reject reciprocal thyroid transplants, despite the acute rejection of reciprocal skin grafts. Thyroid grafts were rejected, however, after presensitizing the recipients with skin graft syngeneic with the thyroid, but not after sensitization with spleen cells. In the present work we induced tumors in bm1 mice by treating them with a chemical carcinogen (3-methylcholanthrene). We found that two out of four tumors demonstrated strict strain specificity and were rejected by all mouse strains (including the B6 recipients) except by their strain of origin. All tumors were found to be sensitive to in vitro lysis by B6 anti-bm1 effector cells. HZ1-A and HZ1-B tumor cells were rejected by B6 recipient mice but could not immunize B6 mice against a subsequent bm1 thyroid graft. When testing the immunogenicity of B6 originated EL4 leukemia cells (which are fatal to B6 mice), we found that the tumor cells were rejected by bm1 recipients, but, unlike B6 skin grafts, were incapable of inducing the rejection of a subsequent B6 thyroid transplant. The results demonstrated that an H-2K molecule may exhibit different immunological properties when expressed on cells of different tissues. The different expression of the mutated antigen on different cell types, its ability to trigger T cells but not B cells responses and the potential involvement of the tissue specific differentiation molecules in the graft rejection response are discussed.

Expression of the teratocarcinoma phenotype in hybrids between totipotent mouse teratocarcinoma and myeloma cells

We have produced somatic cell hybrids between totipotent mouse teratocarcinoma and myeloma cells. These hybrids behave like the teratocarcinoma cell parent and express teratocarcinoma embryonal antigens. However, they also express the myeloma H-2 antigens. THe availability of these hybrids should make it possible to study the expression of already rearranged immunoglobulin genes during mouse development.

Cell surface receptors for ecotropic MuLV: detection and tissue distributions of free receptors in vivo

The expression of available cell surface receptors for binding of the major envelope glycoprotein of Rauscher MuLV, gp71, was studied in freshly prepared tissues of the low-leukemic mouse strain CBA. The presence of such receptors is a requirement for infection and therefore also for transformation of cells in vitro by ecotropic MuLV. This paper describes the conditions of the binding assay for radiolabelled RLV gp71 and freshly prepared lymphoid cells under which binding occurs as a function of time and cell number. With this assay, available receptors for RLV gp71 were detected in all lymphoid as well as some non-lymphoid tissues, most notably brain. The lack of binding in other non-lymphoid tissues was not due to the presence of gp71 specified by endogenous ecotropic MuLV, as was determined by a sensitive group specific RIA. These results demonstrate that the distribution of receptor sites necessary for infection by ecotropic MuLV does not directly correlate with the tissue distribution of malignant transformation that is most commonly induced by these endogenous viruses. Therefore, susceptibility to infection by ecotropic MuLV, as determined by the expression of viral receptors, is not sufficient to determine the target organ for MuLV-induced oncogenesis.

Properties of teratocarcinoma-thymus somatic cell hybrids

A series of teratocarcinoma-thymus hybrid cells (PCT hybrids), which had been shown previously to give rise to multidifferentiated tumors and hence to be pluripotent, was tested to see whether these cells resembled their embryonal carcinoma parent in other ways as well. PCT hybrid cells looked like embryonal carcinoma parent in other ways as well. PCT hybrid cells looked like embryonal carcinoma cells by phase contrast and electron microscopy, have high levels of alkaline phosphatase, and fail to express Thy 1 alloantigen (which is present on thymocyte parental cells, but not on embryonal carcinoma cells). PCT hybrids do, however, exhibit H2 antigens, which are present only at very low levels, if at all, on embryonal carcinoma cells.

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 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.

Histocompatibility studies in a closely bred colony of dogs. 3. Genetic definition of the DL-A system of canine histocompatibility, with particular reference to the comparative immunogenicity of the major transplantable organs

The segregation of the canine DL-A leukocyte group antigen(s) b, c, d, e, f, g, h, k, l, and m has been traced in 141 consecutive matings in the Cooperstown Colony of beagles. All of the leukocyte antigen(s) were regularly transmitted en bloc from parent to offspring, with no instance of independent segregation. A total of 23 haplotypes, including six different DL-A antigen patterns (gl, bkhfm, bkcd, e, be, fgl) was observed. 31 different DL-A phenotypes were observed in a population of 100 mongrel dogs. A number of statistically significant positive and negative associations between individual DL-A antigenic components occurred in this population. The results support the concept of the DL-A system as a complex immunogenetic system governed by a single region (or locus) of an autosomal pair of chromosomes. Studies of skin, kidney, heart, and liver allografts in the Cooperstown Colony indicated that the longest allograft survivals occur under genetically and serologically defined conditions of donor-recipient DL-A compatibility. Skin and renal allografts generally behaved in parallel fashion, while cardiac allografts survived for longer periods of time (MST = 47.1 days) than kidneys (MST = 28.1 days) or skin (MST = 25.1 days) under conditions of DL-A identity. Heart transplants were rejected at a more rapid rate than kidney, however, in DL-A-incompatible donor-recipient combinations. Liver transplants were accorded the longest survival time (MST = 76.2 days) under conditions of DL-A identity, but were rejected at a rapid rate (MST = 5 days) in DL-A-incompatible nonlittermate donor-recipient pairs. The results provide further evidence that the DL-A system is the principal system of histocompatibility in the canine species. The differences in survival of different organs under similar conditions of donor-recipient DL-A compatibility suggest, however, the existence of a number of unknown variables which may also be capable of significantly affecting allograft behavior.

Histocompatibility studies in a closely bred colony of dogs. II. Influence of the DL-A system of canine histocompatibility upon the survival of cardiac allografts

The DL-A system of histocompatibility plays an important role in conditioning the survival of cardiac allografts in the unmodified canine host. The mean survival time of six cardiac allografts performed in DL-A-compatible littermate dogs obtained from a closely bred colony of beagles was 53.2 days, while the MST of transplants performed in seven DL-A-incompatible animals was 7.3 days. The MST of cardiac allografts performed in nine DL-A-compatible nonlittermate beagles was 26.3 days, as compared with 6.3 days in six DL-A-incompatible nonlittermate transplants. The results did not appear to be affected by Swisher erythrocyte-group incompatibilities. The MST of 28 cardiac allografts performed in randomly selected mongrel dogs was 10.0 days. Incompatibilities for DL-A antigens e, f, g, l, and m may constitute major barriers to transplantation, but antigens b, c, d, and k appeared to act as weak histocompatibility antigens. Under controlled conditions of donor-recipient DL-A compatibility, cardiac allografts may be less immunogenic than renal transplants. Heart transplants performed across major donor-recipient DL-A incompatibilities appeared, however, to be more vulnerable to the events of allograft rejection than renal allografts performed under similar conditions. The selection of optimally compatible donor-recipient combinations for organ transplantation may be aided materially by genetic studies of the transmission of DL-A antigens to the animals under consideration.

Antigenic structure of cell surfaces. An immunoferritin study of the occurrence and topography of H-2' theta, and TL alloantigens on mouse cells

The representation of mouse alloantigens belonging to three systems, H-2, theta and TL, on the surface of cells from thymus, spleen, lymph nodes, and peritoneal cavity, was studied by electron microscopy with ferritin-labeled antibody. As expected from earlier serological data, TL was confined to thymocytes, theta was found on thymocytes and lymphocytes, and H-2 occurred to some extent on all cell types observed. On reticular cells, lymphocytes, plasma cells, and eosinophils, the majority of the cell surface was occupied by H-2; thymocytes had considerably less H-2, and erythrocytes and peritoneal macrophages least of all. In every instance the representation of antigen was discontinuous, the fraction of the cell surface covered being characteristic both of the antigen and of the type of cell. H-2 and theta provide a striking example of this; H-2 is present in far higher amounts on lymphocytes than on thymocytes, whereas the converse is true of theta. Within areas positive for H-2 or theta, protuberances of the surface membrane were often antigen-negative. A better definition of cell surface structure, gained from studies such as this, is necessary for further inquiry into how the cell surface is assembled, and into selective gene action in relation to cellular differentiation.