A high proportion of sera of heroin addicts possesses anti-HLA class I and class II reactivity.

The anti-HLA reactivity of sera from 210 heroin addicts was tested by the direct binding with 125I-labeled preparations of HLA class I and class II molecules purified from human B-cell lines of various HLA haplotypes. A high proportion (81.7%) of the sera tested possessed anti-HLA class I and II reactivity.

HLA typing data on 100 type 1 (insulin-dependent) diabetic patients from central Italy show a negative association with DR5 rather than with DR2.

HLA typing of 100 Type 1 diabetic patients from the Rome area confirmed the strong association with DR3 and DR4 and the prevalence of DR3/4 heterozygotes. However, DR5 rather than DR2 showed a significantly negative association.

Radioimmunoassay typing gives a more precise definition of the HLA association of type 1 (insulin-dependent) diabetes.

The problem of the HLA association of Type 1 (insulin-dependent) diabetes was re-examined by testing Class II antigenic specificities detectable by radioimmunoassay. Established (DRw53, DQw1, DQw2, DQw3) as well as newly described (DC5, DCalpha3) specificities were typed. The data obtained suggest that the association with DR3 and DR4 is secondary to that with DQ specificities in linkage disequilibrium with DR3 and DR4.

Specificity of rabbit antibodies elicited by related synthetic peptides.

Three 17-residue peptides, presenting from 65% to 70% sequence homology, and one endecapeptide, with no apparent homology with the first three, were chemically synthesized and investigated in their ability to elicit rabbit antipeptide antibodies. The complex cross reactivities of the antisera were investigated by testing the binding of the antibodies to the intact peptides, to their enzymatic fragments, and by the use of specific immunoadsorbents. Antipeptide antibodies may or may not crossreact with related "parent" peptides, this depending upon number, distribution, and localization of amino acid differences in low or high antigenicity regions of the immunogen.

Identification of anti-DQ alloantisera correlated with DR5.

Using classical serological methods, we have been able to distinguish anti-HLA-DR from anti-DQ antibodies. The specificity of alloantisera for DQ could be identified on the basis of differential reactivity against B cell and monocyte-enriched leucocyte suspensions and lack of inhibition of cytotoxicity by anti-DR monoclonal antibodies. Some alloantisera, whose reactivity was significantly correlated with DR5, were found to exhibit these characteristics.