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Qualitative and/or quantitative alterations in the expression of the MHC class II molecules affect the onset and maintenance of the immune response and may be the basis of a wide variety of disease states, such as autoimmunity and immunodeficiency.CIITA is a major physiological regulator of the expression of MHC class II genes. The availability of CIITA ap- pears generally essential for MHC class II gene expression, and hence its own transcriptional regulatory mechanisms result of fundamental importance for a correct homeostasis of the immune response. Therefore, it is possible to hypothesize that variability at the CIITA-encoding locus, AIR-1, could constitute an additional source of susceptible traits to autoimmune diseases. Mutations at AIR-1/CIITA promoters could modulate expression of CIITA. Variations in CIITA expression could influence the qualitative and quantitative expression of MHC class II molecules at cell surface. We have analyzed sequence variation at AIR-1/CIITA promoters by PCR-SSCP in 23 IDDM and 30 RA patients compared to a sample of 19 unaffected normal controls and 16 unaffected IDDM family members, for a total of 88 Caucasian subjects from the Northeast of Italy. No sequence difference was found at the four AIR-1/CIITA promoters between autoimmune patients and normal controls. Moreover, the promoters resulted invariant within the entire group of 88 subjects analyzed, comprising patients and controls. This finding suggests a possible selective advantage in maintaining CIITA upstream regulatory sequences invariant.

Since 1996 the Immunogenetics Laboratory of the National Cancer Institute/CBA, Genoa, in collaboration with the Immunohematology Research Centre of Bergamo has organized on behalf of Associazione Italiana di Immunogenetica e Biologia dei Trapianti (AIBT) and Istituto Superiore di Sanità (ISS) the quality control programme of HLA genomic typing for class I and II antigens for the laboratories performing HLA typing for organ and bone marrow transplantations. Herewith are reported the results and comments to the 1997 quality control programme along with some overall data.

IgA deficiency (IgA-D) represents the most common immunodeficiency syndrome of infancy. In most cases IgA-D represents an isolated immunological disorder, while sometimes it is associated with IgG subclass deficiency or with the presence of autoantibodies. We investigated the pattern of association of IgA-D with DRB1 and DQB1 loci of the HLA region by DNA molecular typing, which allows the identification of previously serologically undefined specificities. We also compared the gene frequency of DRB1 and DQB1 allelic variants between IgA-D subjects with or without serum autoantibodies. Our results indicate that the gene frequency of the DRB1*0102 subtype and of the DRB1*0102, DQB1*0501 haplotype is significantly higher in IgA-D than in the general population. Furthermore, the IgA-D subjects with autoantibodies showed a positive association with DR4 and DR13 subtypes, thus supporting the hypothesis that genetic factors are also involved in the association between IgA-D and autoantibodies.

In the present report, we describe a DNA typing method that allows detection of all the polymorphic variants of DQA1 and DQB1 second exons. By the oligotyping procedure provided in this paper, we are able to identify 8 DQA1 and 13 DQB1 alleles and to type random individuals in any heterozygous combination. We provide the hybridization and washing temperatures for using either 32P labelled or non-radioactive probes. The discrimination power of this procedure, compared to serological and cellular techniques, is remarkable. Therefore, this typing method finds perfect application in transplantation immunology and it will be very helpful to optimize the matching of unrelated donors before BMT. It is apparent from our results that despite the linkage disequilibrium present between DQ and DR loci, a DR specificity may frequently be associated to different DQ haplotypes. This is the case for DR4, DR7, DR8, DR9, and DR13 specificities.

HLA-DQA1 typing of 227 randomly selected Northern Italian people by the use of polymerase chain reaction are reported. The combined use of commercial Amplitype HLA-DQalpha system and four sequence-specific oligonucleotide probes allows the definition of 8 alleles and 36 genotypes, arranged according to World Health Organisation nomenclature. Seven of these genotypes are not observed among the analyzed samples. Allele frequencies range from 1.5 to 35.7% and genotype observations do not deviate significantly from Hardy-Weinberg equilibrium; observed heterozygosity is 0.8238 with an allelic diversity value of 0.79 and the power of discrimination is 0.925. Our Italian population sample shows differences from other Caucasian samples both for allele and genotype frequencies. This locus typing for the 8 defined alleles provides a rapid and sensitive method in individual identification and paternity investigation.

The HLA antigen and gene frequencies (A, B and C loci) in the populations of the Bergamo area and of the Campania region are compared. Significant discrepancies were found between the two sets of data, as regards the distribution of single genes and the haplotype frequencies and deltas as well. Stone of the frequencies diverge significantly also from accepted data on European Caucasoid populations.

Two 8th Workshop alloantisera, 8W1062 and 8W614, which were classified respectively as anti-DR5 and anti-DR3, were found to react with an Ia preparation from LG38 cells (DR5,5) that was depleted of DR and BR molecules and enriched in DC molecules by pretreatment with a monoclonal antibody and an antiserum against alpha-subunits of DR and BR molecules. The reaction of both alloantisera was inhibited by DR3-positive, DR5-positive, and DRW13-positive individuals. This pattern does not correspond to any of the hitherto reported supertypic specificities. Both antisera were shown to bind to the alpha-subunit isolated from the DC-enriched preparation but not to the beta-subunit. The specificity has been named DC alpha 3. Family studies show the segregation according to the HLA haplotype patterns. This demonstrates by formal genetics criteria the HLA linkage of the locus controlling the DC alpha-subunit.

The HLA-A, -B and -C locus gene frequencies and the significant A, B and B, C haplotypes of the population of Campania (Southern Italy) are reported. From a comparison of gene frequencies and from an overall genetic distance evaluation with other European and Mediterranean populations the typical Mediterranean structure of the Campanian population is confirmed. While keeping several Middle Eastern features, it places itself as far from Northern Italy (Bergamo) as from the Spanish and the French populations. Among all the groups compared, including Turkish and Lebanese, the largest distance is measured from the English, the Danish and the German populations.

Using two alloantisera produced by planned immunization of blood donor volunteers, a new specificity was defined residing on human Ia molecules. The specificity is possessed by the following human lymphoid cell lines: Reh, NALM-1, B89, KM-3 and BJAB, and appears to be the same as the DRw13 specificity discovered in the 8th International Histocompatibility Workshop. A radioimmunoassay for typing w13 on peripheral blood lymphocytes was established. A population and family study supports the genetic control by the HLA-DR locus. The phenotypic frequency in an Italian population was 3.7 percent. The relationship between w13 and the MT2 supertypic specificity was confirmed at the molecular level and the papain sensitivity of w13-carrying molecules was determined.

Polymorphism of mitochondrial DNA has been studied in two highland (Desulo, Tonara) and in two lowland (Galtellì, Orosei) Sardinian isolates, formerly subjected to different selective pressure due to malaria, and in 103 individuals from Northern Italy (Bergamo area), where malaria never appeared to be endemic. Two mitochondrial restriction endonuclease patterns (morphs) never described before have been found, one in the Bergamo and Orosei samples, and the other one only in Orosei. Four new mitochondrial types (mitotypes) due to different combinations of morphs have been identified; two of them have been found only in Sardinia, but with such a low frequency that they cannot be defined as typical Sardinian mitotypes. One mitotype (BamHI-morph 3, MspI-morph 4, AvaII-morph 9 and HaeII-morph 1) showed a significantly higher frequency in the highland rather than in the lowland Sardinian villages or in the Bergamo area. Since this mitotype has been found at a relatively high frequency in Central and Southern Italy, while it has been reported to be rare in Caucasians of Central European origin and absent in other ethnic groups (Africans, Chinese, Japanese and Israeli Jews), we suggest it may represent an ancient Mediterranean type. The analysis of these data suggests that drift or other evolutive forces different from malaria might be the major cause of mitochondrial DNA variation in Sardinia.