Aberrant expression of Ia-like antigens on tumor cells of regressing but not of progressing Rous sarcomas

Chicken major histocompatibility complex congenic lines differ in the percentages of lymphocytes bearing CD4 and CD8 antigens

In the experiments to be described two congenic inbred lines CB and CC and two recombinant lines CB.R1 and CC.R1 were used. All four lines differ only in regard to the major histocompatibility complex (MHC). To determine the percentage distributions of the two cell subsets in peripheral blood lymphocytes (PBL) in these lines, monoclonal antibodies to these two antigens were used. By FACScan there were more CD4+PBL in CB and CB.R1 lines (share B-F/B-L region, controlling class I/class II antigens with line CB) than CC and CC.R1, while the reverse was true with CD8+ subsets. There were more CD8+ PBL in the CC and CC.R1 lines and less in CB and CB.R1 lines. The ratio of CD4+ to CD8+ in CB chickens was 3.4 +/- 0.2 and in CC chickens 1.6 +/- 0.1.

v-src oncogene-specific carboxy-terminal peptide is immunoprotective against Rous sarcoma growth in chickens with MHC class I allele B-F12

B(12) haplotype of the inbred chicken line CB (B12/B12) contains, like the bulk of chicken MHC(B) haplotypes, only a single dominantly expressed class I molecule (B-F). The peptide binding motifs for this major B-F12 molecule in chickens of Rous sarcoma regressor line CB (B12/B12) have been determined. Using stringent and relaxed motifs, several peptides were found in the v-src molecule of the PR-RSV-C, but most of these peptides are identical with that of endogenous c-src. Only the v-src C-tail peptide(517-524) (LPACVLEV) contains critical anchor amino acids (valine at positions 5 and 8) and shows a sequence different from the corresponding c-src peptide. This v-src C-tail peptide up-regulates expression of the B-F12 class I molecule on PBL, as assessed by FACS analysis, and stimulates T cell proliferation in a [3H]thymidine uptake assay. A protective effect of the immune response to LPACVLEV against RSV challenge was demonstrated in CB (B12/B12) chickens immunised with peptides encapsulated in liposomes.

Frequency of chicken CD4+ and CD8+ cells. Genetic control and effect of Rous sarcoma virus infection

In chickens from congenic inbred lines CB and CC that differ only in the major histocompatibility complex (MHC), we observed significantly different percentages of CD4+ and CD8+ cells in peripheral blood lymphocytes (PBL) and spleen. Positive cells were detected by indirect immunofluorescence test as analysed by flow cytometry. In both PBL and spleen cell suspensions, the number of CD4+ cells was significantly higher in CB than in CC chickens, whereas in CC birds there was a higher percentage of CD8+ cells than in CB. These statistically significant differences were under the MHC control. We found no statistically significant influence of regressions or progression of Rous sarcoma virus-induced tumours on the percentage of peripheral T cells and on the interleukin-2 production in vitro.

Modulation of MHC antigen expression by viruses and oncogenes

It is becoming increasingly clear that regulation of MHC antigen expression by viruses and oncogenes, leading to either immune evasion or autoimmunity, is widespread and important in disease. At a recent meeting*, which brought together workers interested in tumour immunology, viral infection and the MHC, a number of mechanisms for the regulation of MHC antigen expression were revealed and the importance of balanced expression of MHC gene products to effective immunity was underlined.

Major histocompatibility complex class II antigen expression during potentiation of line-10 tumor immunity after intralesional administration of bacillus Calmette-Guérin

Intralesional injection of BCG into an established line-10 hepatocellular carcinoma in the strain-2 guinea pig causes regression of the tumor and induction of line-10 immunity. We found that the animals were already protected for a second challenge with line-10 tumor cells 7 days after BCG treatment. We studied whether this early induction of immunity was correlated with the expression of MHC class II antigens on line-10 tumor cells and was correlated with an increased expression of MHC class II antigens on leukocytes in the primary tumor and in the regional lymph node (Ln. axillaris accessorius). The MHC class II antigens and the leukocyte subpopulations were measured with monoclonal antibodies and flow cytofluorometry. In the draining lymph node the number of nucleated cells increased about 10-fold during the first 5 days after intralesional injection of BCG. At this time the MHC class II antigen expression of these cells was increased from 21%-32% in the naive controls to 39%-53% in animals with BCG-treated tumors. This implies that the number of MHC-class-II-positive cells increased about 20-fold in the draining lymph node. Surprisingly, the increase in percentage of MHC-class-II-antigen-positive cells was mainly due to an increase of IgM-positive B cells from 8%-11% to 22%-41% and an increase of IgG-positive B cells from 7%-27% to 25%-44%. In the tumor, BCG treatment induced a small increase of MHC-class-II-antigen-positive cells from 11%-12% to 15%-20%. Probably this increase came not from tumor cells but mainly from a BCG-induced infiltration of mononuclear cells, as an increase of T cells from 14% to 20%, an increase of macrophages from 8% to 18%, and an increase of B cells from 0 to 6% was observed. We conclude that the potentiation of anti-(line-10 tumor cell) immunity correlated with a 20-fold increase of MHC-class-II-antigen-positive cells in the lymph nodes and a small increase in the number of MHC-class-II-antigen-positive tumor-infiltrating cells.

Influence of the major histocompatibility complex on tumor regression and immunity in chickens

A number of studies show that major histocompatibility complex (MHC) genes control host immune responses to viral-induced chicken tumors. The MHC gene-controlled responses to malignant neoplasms caused by Rous sarcoma virus, lymphoid leukosis virus and Marek's disease virus are reviewed. Genes that determine regression of Rous sarcomas and resistance to development of lethal Marek's disease lymphomas appear to map within the B-F region of the MHC. In some cases, genetic complementation of both MHC genes and non-MHC genes may be responsible for regression of tumors. Metastasis of Rous sarcoma cells is also influenced by the host's MHC genotype. Background genes can modify the specific MHC gene effect on resistance to progressive growth of Rous sarcomas and Marek's disease lymphomas. Studies showing that MHC-restricted immunity may be important in cytotoxic T cell reactions to virus-infected and/or transformed chicken cells are discussed. The MHC-restricted cytotoxicity, whereby the T cells and target cells must share one MHC haplotype for in vitro killing to occur, suggests that the T cells have receptors that recognize virus-altered self MHC antigens. This may be an important immune surveillance mechanism for limiting the proliferative growth of virus-induced tumors in chickens.