Five new histocompatibility antigens, designated secondary B cell or (SB) antigens, have been identified by secondary allogeneic proliferative and cytotoxic responses. The reagents used to define the SB antigents are lymphocytes primed between donors matched for all known HLA antigens. The SB antigens stimulate weak primary allogeneic proliferative responses (a mean relative response of 8%) but strong secondary proliferative responses. Strong secondary cell-mediated cytotoxicity is generated against target antigens that are distinguishable from the SB antigens defined by proliferation. Studies by direct lysis and by cold-target inhibition indicate that these target antigens are preferentially expressed on B cells relative to T cells. The SB antigens segregate with HLA, and the gene(s) encoding the SB1, 3, and 4 antigens maps centromeric to HLA-B. The SB antigens are major histocompatibility antigens not only because they are encoded by major histocompatibility complex (MHC) genes, but also by the functional criteria that the proliferative and cytotoxic responses to SB antigens are not restricted by HLA-DR or HLA-A,-B. Parallel studies of the SB antigens and the DR antigens with respect to: (a) their preferential expression on B cells, (b) their function in secondary allogeneic proliferative and cytotoxic respones, and (c) the location of their structural gene within the MHC. However, the SB antigens and the DR antigens are clearly distinct antigens, because population studies indicate that they can occur independently, and family studies indicate that specific SB antigens segregate with HLA haplotypes having different D and DR specificities. Our data are consistent with the hypotheses that the SB antigens are a new segregant series of B cell alloantigens, and that the SB gene and the DR gene derive from a duplicated ancestral gene.

Antibodies to Plasmodium falciparum are classically measured using the enzyme-linked immunosorbent assay (ELISA). Although highly sensitive, this technique is labor-intensive when large numbers of samples must be screened against multiple antigens. The suspension array technology (SAT) might be an alterative to ELISA, as it allows measurement of antibodies against multiple antigens simultaneously with a small volume of sample. This study sought to adapt the new SAT multiplex system for measuring antibodies against nine malarial vaccine candidate antigens, including recombinant proteins from two variants of merozoite surface protein 1, two variants of apical merozoite antigen 1, erythrocyte binding antigen 175, merozoite surface protein 3, and peptides from the circumsporozoite protein, ring erythrocyte surface antigen, and liver-stage antigen 1. Various concentrations of the antigens were coupled to microspheres with different spectral addresses, and plasma samples from Cameroonian adults were screened by SAT in mono-and multiplex formats and by ELISA. Optimal amounts of protein required to perform the SAT assay were 10-to 100-fold less than that needed for ELISA. Excellent agreement was found between the single and multiplex formats (R > 0.96), even when two variants of the same antigen were used. The multiplex assay was rapid, reproducible, required less than 1 l of plasma, and had a good correlation with ELISA. Thus, SAT provides an important new tool for studying the immune response to malaria rapidly and efficiently in large populations, even when the amount of plasma available is limited, e.g., in studies of neonates or finger-prick blood.

We examined B-lymphocyte alloantigens in 41 patients with systemic lupus erythematosus and 184 controls, using a panel of 47 pregnancy serums, and compared reaction frequencies of individual serums. One serum, la-715, reacted with B lymphocytes from 75.6 per cent of patients and 14.1 per cent of controls (Pc less than 0.005, relative risk 18.8). Twenty-eight of the patients were also typed with a panel of HLA-D-related serums from the Seventh International Histocompatibility Workshop, HLA-DRw types assigned, and compared to 490 Workshop controls. Both HLA-DRw2 (57.1 per cent vs. 26.4 per cent, Pc less than 0.004) and HLA-DRw3 (46.4 per cent vs. 22.2 per cent, Pc less than 0.03) were increased in systemic lupus erythematosus. This study demonstrates that select B-lymphocyte alloantigens, which are controlled by genes in the major histocompatibility complex, are present in increased frequency in systemic lupus erythematosus.

To examine the genetic diversity in west Africa, class I HLA-A and HLA-B alleles of 92 unrelated individuals from two areas in the Cameroon, the capital Yaoundé and the village of Etoa, were identified by direct automated DNA sequencing of exons 2 and 3 of the HLA-B locus alleles and sequence-specific oligonucleotide probe (SSOP) and/or sequencing of the HLA-A locus alleles. HLA-A*2301 (18.7%), A*2902 (10.4%), B*5301 (10.9%), and B*5802 (10.9%) were the most frequently detected alleles, present in at least 10% of the population. A total of 30 HLA-A locus and 33 HLA-B locus alleles, including six novel alleles, were detected. The novel alleles were HLA-A*03012, A*2612, A*3006 and HLA-B*1403, B*4016, and B*4703. HLA-B*4703 contains a novel amino acid sequence that is a combination of the first 5 amino acids of the Bw6 epitope and the last 2 residues of the Bw4 epitope. The addition of 6 alleles to the ever-expanding number of known class I HLA alleles supports our hypothesis that extensive genetic diversity, including previously undescribed alleles, would be observed in this African population. In the Yaoundé population, the allele frequency distribution at the HLA-A locus is consistent with distributions indicative of balancing selection. Extensive HLA-A-B haplotypes were observed in this population suggesting that only a fraction of the Cameroon HLA-A-B haplotype diversity has been observed.

No abstract