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A supratype analysis of a North Italian population was performed, using 16 polymorphisms in the HLA region spanning the HLA-A-DP segment. Fourteen supratypes were identified, mostly corresponding to those found in other Caucasoid populations. The degree of their conservation both within the B-DR/DQ region and in the regions telomeric and centromeric from HLA-A and DP was evaluated and linkage disequilibria among several DR and DP alleles were identified. Notably, the degree of association with DP increased when the DR marker was part of a conserved B-DR/DQ supratype. These data are relevant to the definition of the genetic structure of the population and to the prediction of probabilities of histocompatibility matching between unrelated individuals.

The NcoI RFLP of the tumor necrosis factor (TNF) beta gene was analyzed in a panel of 105 unrelated healthy Italian blood donors. The gene frequencies of the 10.5 kb and 5.5 kb allele were 0.73 and 0.27, respectively. The 5.5 kb band was significantly positively associated with HLA-A1, B8, DR17.1, and C4AQ0, and negatively associated with DR7.2, DQw9 and C4A6, all being specificities which belong to two well-known Caucasoid ancestral haplotypes. When the population was subdivided on the basis of TNF phenotypes, different linkage disequilibria between HLA alleles were detected in the three phenotypic classes. From this analysis it was possible to relate preferential HLA associations, most of which are characteristic of ancestral haplotypes, to TNF polymorphism.

Background: Reduced expression of HLA class I molecules has been demonstrated for many human neoplasias and is correlated with increased malignancy., Methods: We investigated the correlation between HLA expression on blasts and the number of peripheral blood leukocytes (WBC) at onset in 34 patients with acute non lymphoblastic (ANLL) leukemia. Leukemic blasts at onset were serologically typed for HLA-A,B specificities, and the patients were classified in three groups according to the number of detectable surface HLA antigens., Results: The amount of WBC at onset in patients lacking HLA antigens was significantly higher than in patients with no antigenic loss., Conclusions: A decrease in HLA class I molecules on the cell surface is correlated with a greater expansion of the leukemic clone.

Nineteen patients that had developed hypertrophic scars subsequent to thermal injury were typed for HLA class II allogenotypes with the restriction fragment length polymorphism technique. A significant association was found with DR beta 16 (pc = 1.45 x 10(-4); relative risk = 12.25). This finding adds evidence to other data suggesting that immunologic phenomena are involved in pathologic scarring. Moreover, the results presented here have allowed an identification of a genetically determined risk factor for hypertrophic scar formation located in the HLA region.

HLA-A,B specificities were analysed on the neoplastic blasts of a panel of 69 lymphoblastic (ALL) and 50 non lymphoblastic (ANLL) acute leukaemias at onset using the standard lymphocytotoxicity technique. Analysis of the number of detected specificities per locus and, when possible, comparison of the results with those obtained on lymphocytes of the same patients during remission revealed many alterations in the expression of A,B specificities including extra specificities both at the HLA-A and -B loci mainly on lymphoblasts and missed specificities mainly at the HLA-B locus on myeloblasts. Lack of A,B antigens was complete in 6.2% of all tested samples (9% of ANLL) and selective for all the products of one locus in 16.8% of all tested samples (27.7% of ANLL). A decrease of class I molecules on the cell surface was evidenced with MoAb W6/32 on blasts missing detectable serological specificities.

Using specific monoclonal antibodies and the indirect immunofluorescence technique, peripheral blood myeloid leukemic blasts from 49 patients were studied for DR expression, 42 for DQ and nine for DP after four days of culture without and with gamma-IFN. The expression of class II molecules on untreated cells depended upon the stage of differentiation and was maximal for DR antigens and lower for DP, while DQ was present only in a small percentage of M2, M4 or M5 blasts. M3 blasts lacked both DR and DQ. Maximal increase of surface expression induced by gamma-IFN was observed for DR molecules independently from the differentiation stage. No significant modification was seen for DQ. Preliminary data concerning DP indicate an increased expression in some of the tested samples. Thus the results obtained on peripheral blood blasts parallel previous observations on leukemic cell lines.

New beta 2-microglobulin (beta 2-m)-associated, HLA-linked alloantigens, selectively expressed on phytohaemagglutinin (PHA)-activated lymphocytes, were identified using human alloantisera. Reactivity of the antisera against activated cells correlated with HLA-A2, A10 and A28 specificities. The new alloantigens were undetectable on peripheral blood mononuclear cells, B lymphocytes and platelets using either the lymphocytotoxicity or the absorption techniques, and appeared on lymphocytes upon PHA activation, with time-dependent kinetics. They were found on some, but not all, acute leukaemias of B, T and myeloid origin, being absent from chronic B lymphocytic leukaemias. The presence of the new beta 2-microglobulin-associated allospecificities was not correlated with the quantity of classical class I antigens present, as analysed on different cell types by flow cytometry. Thus, these antigenic determinants appear to be different from the classical HLA class I antigens and could be the human counterpart of the murine Qa system or of the second H-2K gene.

The expression of class I-like allospecificities on leukemic blasts is not correlated to the amount of HLA-A,B,C molecules, as measured with MoAb W6/32 and IIF, nor with the quantitative expression of HLA-A molecules evaluated by absorption studies.