Specific and sensitive detection of purified HLA molecules in an ELISA using mouse, rabbit and human anti-HLA antibodies

Lack of binding of peptides carrying the human platelet antigen 1 (HPA-1) dimorphism to purified HLA-DRw52a molecules

The strong association between anti-HPA-1a alloimmunization and DR3, DRw52a phenotype in HPA-1b homozygous women suggests that these class II molecules play a crucial role in the immune response against HPA-1a. The diallelic system HPA-1 results in a single amino acid polymorphism at the residue 33 of the glycoprotein IIIa. So, we tested the binding of peptides from the 25-42 region of the GPIIIa to purified HLA-DR3 and -DRw52a molecules, using a solid phase assay and a liquid phase peptide binding assay. No binding was demonstrated, indicating that either the crucial region for binding to class II molecules is not the 25-42 region, or that other events only occurring "in vivo" are required for binding. These results may also suggest an indirect role of the residue 33 for T-cell stimulation.

A simplified cellular ELISA (CELISA) for the detection of antibodies reacting with cell-surface antigens

This paper describes the adaptation of a cellular enzyme-linked immunosorbent assay (CELISA) for the detection of antibodies to cell-surface antigens. This CELISA has the advantages of convenience and rapidity and is therefore ideally suited for the screening of a large number of hybridoma culture supernatants. The basic procedure involves the direct drying of cell suspensions onto the wells of enzyme immunoassay (EIA) plates and a subsequent EIA with appropriate blocking reagents. In order to overcome high background binding of primary antibodies to Fc receptors and of secondary antibodies to surface Ig (sIg), this method involves a blocking step consisting of unlabelled secondary antibodies. Once CELISA plates are prepared, they can be stored for a period of at least 6 months and hence this assay does not rely on the availability of fresh, viable cells for each assay. This assay is simple, reproducible and sensitive. The results can be assessed in an objective manner and can also be adapted for the detection of cellular antigens. This paper describes a CELISA for the detection of antibodies to blood group antigens and human leukocyte (HLA) antigens.

Physical association between MHC class I molecules and immunogenic peptides

Antigenic peptides are presented to T lymphocytes by major histocompatibility complex (MHC) molecules. The binding of peptides to MHC class II molecules has been demonstrated directly, and is found to correlate with the ability of specific class II alleles to restrict the T-cell response to specific peptides. By comparison, a direct demonstration of a physical association between antigenic peptides and MHC class I molecules has proved difficult. A recent report shows that it is possible, however, and the three-dimensional structure of a class I MHC molecule illustrates the site where such binding must occur. Here we describe a simple assay which measures the binding of radiolabelled MHC class I molecules to peptides bound to a solid phase support. We find that class I molecules bind specifically to peptides known to be antigenic for class I-restricted cytotoxic T lymphocytes. Peptides which are recognized by cytotoxic T lymphocytes bind not only to the restricting MHC class I molecule but also to other class I molecules. Our results suggest that quantitative differences in the peptide/MHC class I interaction may influence the-pattern of MHC restriction observed in vivo.