Assignment of gene(s) coding for antigen defined by monoclonal antibody 2B2

The gene for human lymphocyte homing receptor is located on chromosome 11

The mouse monoclonal antibody Hermes-3 recognizes the human lymphocyte homing receptor. A panel of mouse-human T lymphocyte hybrids, carrying all mouse chromosomes and a limited number of human chromosomes, was analyzed for expression of human homing receptor by indirect immunofluorescence and immunoprecipitation of radiolabeled cell lysates with Hermes-3 antibody. Karyotypic analysis of the tested clones showed that the expression of human homing receptor correlated to the presence of human chromosome 11 in all but one clone. However, concanavalin A induced a weak to moderate expression of the homing receptor in this clone, but not in a chromosome 11- clone. Another clone, heterogeneous for the expression of homing receptor, was separated into a Hermes-3+ and a Hermes-3- fraction with a fluorescence-activated cell sorter. Karyotypic analysis performed after sorting showed human chromosome 11 to segregate with the Hermes-3 antigen. To confirm these data we correlated the expression of two chromosome 11-coded antigens, Trop-4 and Leu-7, with the expression of the homing receptor. In our hybrid clones these three antigens were expressed concordantly. The gene coding for the human lymphocyte homing receptor recognized by Hermes-3 is thus assigned to chromosome 11.

Expression of human T antigens in interspecies hybridomas

Interspecies hybrids were constructed by fusing normal human male peripheral blood mononuclear cells with BW5147, a HGPRT- thymoma derived from an AKR mouse. Hybrid cells were selected in HAT media in culture dishes containing 1 X 10(7) human red blood cells. Twelve weeks after fusion, hybridomas were diluted to 10-15 cells/well and characterized for their expression of the human immune cell surface antigens HLA-DR, T3, T4, and T8 using fluorescent microscopy and cytographic analysis. More than 70% of the hybrid colonies expressed human T-cell surface antigens. Moreover the specific human repetitive DNA (ALU) bound to DNA sequences isolated from the hybridomas after Southern transfers. However, the same hybrids did not have a statistically significant increase in their chromosome number when compared to the mouse parent cell line. Several of the hybridomas produced a soluble factor capable of stimulating the growth of the IL-2 restricted murine cell line CTLL-2 and supported DNA synthesis in human peripheral T-cell populations. Panning experiments demonstrated that the IL-2 producing hybridomas could be enriched by selecting for the human T-cell surface antigen T3. The results presented here indicate that mouse X human hybridomas which express a broad range of human lymphocyte markers can be constructed and maintained in continuous culture for extended periods of time. It also appears that the T3-Ti receptor complex mediates the proliferation of T cells through the T3 molecules linkage to the secretion and/or production of IL-2. The usefulness of interspecific T-cell hybrids as an immunogenetic research tool as well as the significance of the mapping data are discussed.

Genetic assignment of GP90, leukocyte adhesion glycoprotein to human chromosome 21

Intercellular adhesion among human leukocytes involves a cell-surface glycoprotein with an apparent molecular weight of 90,000 which forms complexes with higher-molecular-weight glycoproteins. A monoclonal antibody (60.3) against this glycoprotein blocks induced adhesion. Here we have shown that the antibody reacts with cell clones carrying human chromosome 21 in lymphocyte hybrids between an AKR mouse thymoma (BW5147) and human concanavalin A-activated peripheral blood lymphocytes. Cell sorting by FACS of a hybrid clone heterogeneous in the expression of the antigen identified by the 60.3 antibody yielded a positive fraction expressing the antigen and carrying human chromosome 21, and a negative fraction lacking both the antigen and chromosome 21. The gene coding for the cell adhesion glycoprotein is thus provisionally assigned to chromosome 21.

Assignment of gene for human cell-surface membrane antigen Trop-4 to chromosome 11

The gene (named MF16) for a surface membrane antigen, Trop-4, is assigned to human chromosome 11 on the basis of studies using a mouse monoclonal antibody, immunofluorescence, fluorescence-activated cell sorting (FACS), immunoprecipitation, and mouse-human lymphocyte hybrids. The Trop-4 antigen is present on all human cell lines tested, on peripheral blood monocytes and granulocytes, and on a small fraction of peripheral blood lymphocytes, but is absent from erythrocytes. The Trop-4 monoclonal antibody precipitates an 85,000-dalton glycopolypeptide from hybrid cells containing human chromosome 11. However, in a human cell line expressing this antigen, a larger-molecular-weight species, 100-105,000 daltons was coprecipitated with the 85,000-dalton glycopeptide, and under nonreducing conditions a larger compound of 110-125,000 daltons was obtained. Although the Trop-4 antigen is of similar molecular weight to the Mab-4 and F10.44.2 antigens previously assigned to chromosome 11, it is shown to be different from them.