Role of the major histocompatibility complex in resistance to viral leukemia; its effect on the preleukemic stage of leukemogenesis

The implications for childhood leukemia of infection with adenovirus

Adenoviruses have mechanisms that allow persistence in lymphoid cells and immunoevasion. They downregulate major histocompatibility complex (MHC) class I antigen expression and may trigger an autoimmune reaction against MHC class II antigens through mimicry. Adenoviral persistence could be facilitated by human leukocyte antigens A2 and DR53, thereby allowing a preleukemic clone to escape immune surveillance and progress to leukemia.

Influence of the major histocompatibility complex on age at onset of chronic lymphoid leukaemia

The major histocompatibility complex is one of the interactive factors in the multifactorial model of carcinogenesis. Its main influence in experimental models is on the age at onset of malignancies. We have previously shown a similar effect of homozygosity for HLA-DR53 in CML. In the present study, we investigated 79 patients with CLL and 329 local controls from Germany. In addition to full serotyping, all patients and 116 of controls were also typed by HLA-DRB PCR analysis. The homozygosity rates for DR53 in patients under and over the median age (60 years) were 18.6% and 2.9%, respectively (p = 0.03). Eight of the 9 homozygous patients were under the median age. The sex ratio in the DR53 homozygous group was reversed in favour of females. The homozygosity rates for DR53 were different in the overall groups of patients and controls, yielding a relative risk (RR) of 2.4 (p = 0.03). This association was stronger in the early-onset group compared to age-matched controls (RR = 4.4; p = 0.008) and for females with an early onset compared to age- and sex-matched controls (RR = 17.9; p = 0.0008). The simultaneous occurrence of the alleles of the haplotype A2B62DR4 showed a strong association with CLL (RR = 4.1; p = 0.002). This was probably the reason behind the association with HLA-DRB1*0401 (RR = 2.4; p = 0.009). Compared to the accelerating effect of HLA-DR53, HLA-DR52 showed a significant delaying effect on the onset of CLL. These findings confirmed the influence of the HLA complex on the development of another leukaemia.

Major histocompatibility complex and human papillomavirus type 16 E7 expression in high-grade vulvar lesions

To determine whether expression of the human papillomavirus (HPV) type 16 E7 open reading frame influences expression of major histocompatibility complex (MHC) antigens on the surface of squamous epithelial cells, serial frozen sections from seven HPV type 16-positive, high-grade vulvar intraepithelial neoplasia (VIN 2-3) lesions were tested for viral transcription by RNA-RNA in situ hybridization, for MHC expression by immunohistochemical staining with antibodies to MHC class I and II molecules, and for keratinocyte differentiation by immunohistochemical staining with anti-filaggrin and cytokeratin 10 antibodies. Despite the histologic appearance of high-grade VIN lesions, expression patterns of cytokeratin 10 and filaggrin suggested a certain degree of keratinocyte differentiation in all specimens. These differentiation markers were especially prominent in parakeratotic and hyperkeratotic superficial areas, which did not express MHC antigens or contain E7 mRNA. Expression of MHC class I molecules within dysplastic tissues was greater than within HPV type 16-negative, normal vulvar epithelium from the same patients. In five of the VIN 2-3 specimens anti-MHC class I antibodies reacted more strongly with cells of the basal and suprabasal layers than with cells of the epithelial surface. In one lesion basal cells stained less intensively than surface cells, whereas in another specimen all epithelial layers were equally MHC class I positive. Staining with anti-MHC class II antibodies was generally restricted to isolated foci, representing invading lymphocytes, tissue macrophages, and Langerhans cells. In two lesions, however, there was heterogeneous keratinocyte expression of MHC class II proteins, perhaps due to inflammation. Major histocompatibility complex antigen detection was independent of the presence or distribution pattern of E7-specific transcripts. Hence, a correlation between MHC and E7 expression appears unlikely in warty VIN lesions.

Prolongation of survival in retrovirally induced T cell lymphoma by dietary omega 6 fatty acid

C57BL/Ka mice were fed diets rich in omega 3 or omega 6 polyunsaturated fatty acids and inoculated with the thymic lymphoma-inducing retrovirus RadLV. Mice receiving the omega 3 diet died significantly sooner than those receiving the omega 6 diet. Of the three known mechanisms by which fatty acids can exert antiviral activity, namely, modification of membrane fluidity, modulation of immune response, and synthesis of metabolites with antiviral activity, the first two can be eliminated in the model under study. It is therefore concluded that differences in survival are due to fatty acid metabolites with distinct antiviral activities.

Association between BoLA and subclinical bovine leukemia virus infection in a herd of Holstein-Friesian cows

The role of the bovine major histocompatibility system (BoLA) in subclinical bovine leukemia virus (BLV) infection was investigated in a herd of Holstein-Friesian cows (n = 240). The BoLA W8.1 allele was negatively associated with the presence of antibodies to the major BLV envelope glycoprotein, BLV-gp51 (corrected P less than 0.001, relative risk = 0.31). These results suggest that a BoLA-linked gene(s) may influence the early spread of BLV infection. Since B cells are the primary target of BLV infection, we then determined the relationship between BoLA-A locus phenotypes and B-cell numbers in peripheral blood of seropositive and seronegative cows. There were no significant differences between BoLA-A alleles for any hematological parameter in seronegative cows. Seropositive cows with the W12.1 allele had significantly greater absolute numbers of lymphocytes per microliter and B cells per microliter than did seropositive cows with other BoLA-A phenotypes (P less than 0.01, respectively). The average effect associated with the W12.1 allele in BLV-infected cows was an increase of 2010 B cells per microliter of whole blood relative to BLV-infected cows with other BoLA-A phenotypes. These results demonstrate that susceptibility to the polyclonal expansion of BLV-infected B lymphocytes is associated with the W12.1 allele in Holstein-Friesian cattle. Compared with results of a previous study in a herd of Shorthorn cattle, it appears that resistance and susceptibility to subclinical progression of BLV infection are associated with different BoLA-A locus alleles in different cattle breeds.

Recognition of T-cell murine leukemia by bacteriocin (colicin); correlation with transplantation experiments

The presence of potential murine leukemia and overt leukemia cells in various organs at different phases of leukemogenesis was demonstrated by transplantation experiments and sensitivity to bacteriocin (colicin HSC10). Such correlation was found in three experimental models: AKR mice developing spontaneous T-cell leukemia and BL/6 mice infected with radiation leukemia virus variants inducing a high or low overt T-cell leukemia incidence. The sensitivity to bacteriocin was evaluated by testing the cell cycle perturbation following in-vitro incubation of lymphoid cells with colicin (or Tris buffer as controls) monitored by flow-cytometry. The analysis was based on measuring relative differences in fluorescence intensity of propidium iodide stained DNA in the individual cells. The interaction with colicin of leukemic cells and lymphoid cells containing potential leukemic cells (PLC) resulted in a reduction in the cell number of the G0/G1 and SG2M phases while cells accumulated in the "pre-G1" channels. In contrast, normal lymphoid cells exposed to bacteriocin did not show such changes in the DNA histograms. The distribution pattern of PLC in the thymus and spleen (in the models tested) obtained by transplantation studies coincided with sensitivity of spleen and thymus cells to colicin. However, in most instances, the PLC in the bone marrow were not recognized by colicin, but their leukemogenic potential was reduced following interaction with colicin as shown by PLC transplantation studies. It is thus suggested that colicin might be used for identification and eradication of transformed cells.

Bone marrow phenotype determines genetic resistance to RadLV-induced leukemia in radiation chimeric mice

The development of RadLV-induced T-cell leukemia is a multistep process which evolves along the bone marrow-thymus axis. This process has been shown to be under the control of resistance and susceptibility genes. The relative importance of bone marrow and thymic phenotypes in this genetic control have not been established. We have constructed radiation chimeras with bone marrow from susceptible C57BL/Ka and thymus from resistant B10.A(5R) mice (and vice versa). The rate of leukemia development in the various groups indicates that the phenotype of the bone marrow and not that of the thymus determines the expression of resistance or susceptibility.

Evidence for BoLA-linked resistance and susceptibility to subclinical progression of bovine leukaemia virus infection

The role of the bovine major histocompatibility complex in bovine leukaemia virus (BLV) infection and disease progression was investigated in a herd of Shorthorn cattle (n = 117). The frequency of cows that were seropositive to BLV-glycoprotein antigen was 51%. Twenty-three per cent of the seropositive cows were lymphocytotic. At the herd level, relative resistance to BLV-dependent B-cell proliferation and lymphocytosis among seropositive cows was associated with bovine lymphocyte antigen (BoLA)-DA7, whereas susceptibility was associated with BoLA-DA12.3. These associations were also confirmed at the family level, where BoLA phenotypes were used as haplotypic markers. Among the offspring of one BoLA-heterozygous sire (n = 33), resistance segregated with the DA7 haplotype and susceptibility with the DA12.3 haplotype. In this sire group, maternal transmission of the BoLA-w8 allele was associated with increased susceptibility to B-cell proliferation and lymphocytosis in w8/DA12.3 heterozygotes. These data provide the first evidence that subclinical progression of BLV infection is under the control of the BoLA complex, and suggest that the BoLA system can be used to select for resistance to B-cell proliferation and the development of lymphocytosis in BLV-infected herds.

Imbalanced MHC class II molecule expression at surface of murine B cell lymphomas

To study the role of class II MHC expression in mouse lymphomagenesis, we examined the cell surface expression of I-A/E antigens on 24 spontaneous or murine leukemia virus (MuLV)-induced mouse B10.A (I-Ak, I-Ek) B cell lymphomas. Two primary B10.A B cell lymphomas were observed with strong I-Ek expression but with only minimal cell surface I-Ak expression. Both tumors are readily transplantable in syngeneic mice, with maintenance of their I-A-, I-E+ phenotype. Strikingly, one I-A-, I-E+ B cell lymphoma contains a (11; 17) translocation with a breakpoint on chromosome 17 that is localized within or very close to the H-2 complex. DNA of both tumors contains normal restriction enzyme fragments of the A alpha and A beta genes. Northern blot analyses indicated that one I-A-, I-E+ tumor strongly expressed A alpha, E alpha, and E beta mRNAs but possessed only a weak expression of A beta mRNA. The other B cell lymphoma showed A beta, E alpha, and E beta mRNA expression but only minimal A alpha mRNA expression. In 11 primary B10.A B cell lymphomas with a normal I-A+, I-E+ phenotype, no imbalances in A alpha/A beta mRNA levels were observed. The implications of these findings for the role of class II MHC expression in mouse B cell lymphoma-genesis are discussed.

Expression of major histocompatibility antigens and nature of inflammatory cellular infiltrate in ovarian neoplasms

Expression of histocompatibility antigens and the intensity of inflammatory cellular infiltrate were evaluated in frozen tissue sections from 70 human ovarian tumors and six normal ovaries using monoclonal antibodies and an avidin-biotin immunoperoxidase technique. In the normal human ovary, surface epithelial cells, mature granulosa cells and lutein cells reacted with anti-HLA-A,B,C (HLA) and beta2-microglobulin antibodies but not with anti-Ia (Ia-like, HLA-DR). Stromal cells and granulosa cells of the primordial follicles did not react with any of the antibodies. Among the neoplasms examined, all benign epithelial tumors, 86% of borderline an 81% of malignant epithelial tumors reacted with anti-HLA and/or beta2-microglobulin antibodies. HLA-negative epithelial tumors were of serous or endometrioid types. Although Ia was not found in normal ovarian surface epithelium, the antigen could be detected in 44% of benign, and 43% of borderline and malignant epithelial ovarian tumors. Mononuclear cellular infiltrate was generally scarce in ovarian tumors and consisted mainly of T cells. Malignant epithelial tumors contained significantly more T cells than did benign tumors. More T cells were observed in HLA-positive ovarian tumors than in HLA-negative neoplasms, but the difference did not achieve statistical significance. No correlation could be found between Ia expression and the intensity of T-cell infiltrate. Significantly more T8 and Leu-3a-positive cells were found in the tumor stroma than amongst neoplastic cells. HNK-I-positive natural killer cells, OK-MI-positive macrophages and BI-positive B lymphocytes were rarely encountered either in the tumor stroma or between adjacent tumor cells.

Cell lines producing human T-cell lymphoma virus show altered HLA expression

Human T-cell leukaemia/lymphoma virus (HTLV) can be identified in fresh and cultured T-lymphocytes from patients with adult T-cell malignancies. HLA typing of the peripheral blood lymphocytes and cultured cell lines from the patient from which the virus was originally isolated suggested the expression of additional HLA-A and -B locus antigens on the HTLV positive cultured T-cells that were not present on the EBV transformed B-cell line or on the peripheral blood lymphocytes. Peripheral blood lymphocytes (PBLs) and T-cell lines established from patients and cord blood lymphocytes, infected with virus by co-culture with T-cell lines, were typed for HLA antigens with alloantisera and in addition tested for reactivity with a monoclonal antibody (4D12) which recognizes a polymorphic HLA class-I antigen. In all HTLV positive cells, with demonstrable provirus replication, altered HLA alloantigen expression was observed. This may be explained by the observations reported in the accompanying paper which shows homology between the envelope gene region of HTLV and the region of an HLA-B locus gene which codes for the extracellular portion of a class I histocompatibility antigen.