Binding of labelled influenza matrix peptide to HLA DR in living B lymphoid cells.

T cells recognize protein antigens as fragments (peptides) held in a defined binding site of class I or class II major histocompatibility (MHC) molecules. The formation of complexes between various immunologically active peptides and different MHC molecules has been demonstrated directly in binding studies between the peptides and solubilized, purified molecules of class II MHC. Studies with intact cells, living or fixed, have not directly demonstrated the binding of the peptides to MHC molecules on antigen-presenting cells, but the formation of such complexes has been shown indirectly through the capacity of antigen-presenting cells to stimulate specific T cells. Here we report evidence that supports directly the binding of radiolabelled influenza matrix peptide 17-29 to products of the human class II MHC locus HLA-DR, on living homozygous B-cell lines, and we show that the kinetics of such binding is much faster with living cells than with fixed cells. Furthermore, whereas the peptide reacts with HLA-DR molecules of all alleles, it binds preferentially to DR1, the restricting element in antigen presentation.

Mitochondrial DNA polymorphism in four Sardinian villages.

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.

Distribution of Ha-RAS-1 proto-oncogene alleles in breast cancer patients and in a control population.

The frequencies of 13 different Ha-ras proto-oncogene alleles have been estimated in 92 breast cancer patients and 60 unaffected individuals. The Ha-ras alleles can be identified using a DNA restriction fragment length polymorphism (RFLP) closely linked to the 3' end of the gene, and are characterized by a different length due to a region of sequences repeated a variable number of times (variable tandem repeats, VTR). The statistical analysis of the data obtained shows that the frequency of alleles ranging between specific length limits is significantly higher in breast cancer patients than in controls. The same applies to specific genotypes bearing the aforementioned alleles. This suggests that the inheritance of these alleles may be associated with an increased risk of developing breast cancer.

Generation and characterization of murine monoclonal antibodies against HLA Class II molecules.

HLA Class II antigens (human la) are coded by Major Histocompatibility Complex and play important biological roles in health and disease. In this report we describe the generation and characterization of nine murine monoclonal antibodies (MoAbs) specific for determinants localized on the human la molecules. The reactivity of these MoAbs inferred from serological analysis along with the data obtained from biochemical characterization of the target structures allowed a classification of these reagents as monomorphic and polymorphic. Two monomorphic MoAbs, identifying different subsets of human la molecules, were studied in detail.

A xenogeneic monoclonal antibody recognizing specificities controlled by HLA-A and B alleles.

In the present paper one reagent among the many prepared has been carefully studied. It is a xenogeneic monoclonal antibody, F10.13/13, obtained by immunizing mice with human peripheral blood lymphocytes. The splenocytes of the immunized mice were fused with a murine were fused with a murine myeloma and the supernatants of the resulting Ig-secreting hybridomas were tested against appropriate targets. --F10.13/13 behaves in a very peculiar manner from the serological point of view and we think that it reacts with maximal affinity with an epitope expressed most strongly on HLA glycoproteins controlled by genes B8, B7, and Aw19.

Modulation of expression of HLA components at the cell surface induced by anti-beta 2m reagents.

Antibodies against lymphocytes surface components are able to rearrange profoundly the topography of the cell membrane with a differential modulation of surface antigens. Of particular interest is the effect of anti-beta 2m reagents, which are able to suppress completely the reactivity of epitopes carried by the two chains of the ABC dimers, while th expressivity of other antigens, such as DR, is significantly increased. These results have been obtained with immunoradiobinding under a variety of conditions, thus confirming the validity of the "bb" (beta 2m blanketing) test.

Quantitative analysis of cell surface HLA structures by means of monoclonal antibodies.

Quantitative data on the binding of murine monoclonal antibodies ot whole human lymphoblastoid lines and peripheral blood lymphocytes (PBL) are reported. Antibodies reacting with beta 2m or a common part of the HLA heavy chains and nonpolymorphic determinants of the DR dimer were used. The equilibrium constant (K) of the reaction and the total number of antigenic determinants was graphically estimated. For the above-mentioned antibodies, K ranged between 5 X 10(8) and 4 C 10(9) l/mole at 0 degrees C and progressively decreased with the increasing temperature. T cells expressed less HLA and beta 2M determinants than the B cells. The number of determinants per surface unit is higher on the B cell from PBL than on E.B. virus-transformed cell lines and is generally very low, suggesting that the complement-dependent cytotoxic activity is a phenomenon depending on membrane fluidity. A portion of beta 2m seems not to be bound to the HLA heavy chains on B cells as well as on T line surface, as already shown for Molt 4 line.

Separation of human cells bearing HLA-DR antigens using a monoclonal antibody rosetting method.

A technique is described for enriching, from human blood, cells bearing HLA-DR antigens. The method depends on the use of monoclonal mouse antibody which reacts with HLA-DR structures. Cells to which this antibody has bound can be separated after rosetting with bovine erythrocytes coated with anti-mouse immunoglobulin. The cells thus enriched may be used for HLA-DR typing by standard cytotoxicity methods with allogeneic sera.

Sacroiliitis and HLA. A clinical and genetical study.

Among 39 patients (23 males, 16 females) with sacroiliitis (SI) 17 were HLA-B27 positive. The female/male ratio in the B27-positive group was 2/15. Seventy-four first-degree relatives of 26 probands were also investigated. A high occurrence of SI (20%) was observed in the families of B27-positive probands compared with only 3.7% in the families of B27-negative probands. In the former families SI occurred only in B27-positive subjects with an earlier onset of symptoms and a male prevalence. In the latter, the disease showed a later onset and a lack of male preponderance. The nosological and prognostic relevance of the B27 typing is stressed.

Appearance and evolution of anti-Da (B cell-specific) antibodies after planned immunizations.

Appearance and evolution of anti-Da antibodies has been followed in eight volunteers immunized by whole blood transfusions or leukocyte intradermal injections form a single donor incompatible for HLA--A,--B,--C and--D specificities. Several unabsorbed bleedings from each recipient were studied against the specific immunizer with three different complement-dependent lymphocytotoxicity (CdL) techniques: (1) standard NIH CdL on total peripheral blood lymphocytes (PBL); (2) VII Workshop standard CdL technique on B cell-enriched suspensions; (3) beta2 microglobulin blanketing test ("bb" test) on B cells. Results obtained with the "bb" test were confirmed with platelet-absorbed sera. The "bb" and the absorbed sera allow discrimination between anti-Da and anti-HLA--A,--B,--C antibodies. Stage of appearance and evolution are rather similar for an anti-HLA--A,--B,--C and anti-Da. An early appearance of antibodies positive only against B cells is due to weak anti-HLA--A,--B antibodies which react better with B cells than with total PBL. Immunogenicity of Da antigens seems to be of the same order as HLA--A, and--B. In fact, Da reactivity was present in all eight recipients studied. These reactivities always segregated in familes with these HLA haplotypes. On a small panel of unrelated D-typed donors, three sera showed a significant positive association with D alleles.

Structural heterogeneity of C2 Complement protein and its genetic variants in man: a new polymorphism of the HLA region.

A zymogram method, following thin-layer isoelectric focusing in a polyacrylamide gel, allows resolution of the lytic activity of serum C2 complement protein in a spectrum of molecular forms. This spectrum is characteristic in each of the species studied (man, rhesus monkey, guinea pig, and hamster). Moreover, two different alternative patterns are observed in man: each of the six major lytic bands characteristic of the most common pattern (herein designated C2(1) is duplicated in the least common pattern (C2(2-1), with an additional band displaced cathodally by not more than 0.04 pH unit. Distribution of phenotypes C2(1) and C2(2-1) in a Caucasion population is in agreement with the hypothesis that they are controlled by two alleles, C2(1) and C2(2), with frequencies 0.96 and 0.04 +/- 0.01. Segregation studies show that the two alleles are codominant and identify a locus in the HLA region. No recombinants with HLA-B were detected among 27 informative meioses, generating a cumulative lod score of 6.321 at equals 0. These findings suggest that the individuals with the C2-deficient trait might be interpreted as homozygotes for a third and rarest amorph C2 degrees of the same locus.

B cell antigens of the HLA system: a simple serotyping technique based on non-cytotoxic anti-beta2-microglobulin reagents.

A modification of the NIH cytotoxicity test for recognizing B cell (D-associated) antigens and antibodies, when sera also contain anti-HLA(ABC) activity is described. The method is based on the observation that anti-beta2-microglobulin reagents are able to block lympholysis only when due to HLA(ABC) antigens.