Loss of HLA-C locus specificities from stored lymphocytes and de novo synthesis following incubation at 37 degrees C

Evidence of a second polymorphic ELA class I (ELA-B) locus and gene order for three loci of the equine major histocompatibility complex

Two antisera, B-442 and R-2046, were produced by immunizing offspring with purified peripheral blood lymphocytes from a parent matched for the ELA-A specificity carried on the unshared haplotype. Absorption analysis demonstrated that these antisera contained at least two families of cytotoxic antibodies, one directed against antigens present on T and B cells, and a second directed preferentially against antigens present on surface Ig positive cells. Immunoprecipitation studies using these antisera demonstrated that both antisera contain antibodies specific for glycoproteins with molecular weights characteristic of class I and class II MHC antigens. In lymphocyte typing tests of unfractionated lymphocytes, only the class I activity was readily detectable since the class II activity killed less than 25% of the cells. Family studies demonstrated that these antisera recognize products of genes linked to the ELA system. Based on two recombinants in an extended family it became apparent that the specificities detected by B-442 and R-2046 are not products of the ELA-A locus, but rather they are products of at least one other locus, defined in this paper as ELA-B. In this family a third recombinant was found between the A blood group system and the ELA-A locus. Based on these three recombinants, the most probable linear relationship of the following genes is: A blood group system/ELA-A/ELA-B.

Definition of HLA-C alleles using sequence-specific oligonucleotide probes (PCR-SSOP)

Many new HLA-C locus alleles have recently been identified by DNA sequencing, and a molecular based method for their detection using PCR with sequence specific primers has been reported. However, other methods may be more appropriate for the identification of C locus alleles in larger studies. Here we describe one such system, based on PCR sequence specific oligonucleotide probes, (SSOP) for C locus typing. Advantages of SSOP typing compared to SSP are that it is easier to detect new alleles, more cost effective and less time consuming. We have developed a DNA typing method to identify the broad C locus antigens (including those not yet defined serologically) using a minimum of probes with one amplification. We use a C locus specific sense primer in exon 2 and a consensus antisense primer in exon 3, in a two-step PCR, giving a product of 710 bp. Probes were designed with similar melting temperatures (54-56 degrees C) that would identify as many alleles as possible. The method was established using DNA from B lymphoid cell lines of known C locus type, mostly 10th workshop homozygous cell lines, plus as many other sequenced cell lines as possible. The system was able to correctly identify their C locus types using only 26 probes. DNA was tested from a panel of serologically typed individuals which included many different heterozygous combinations. We found a high concordance of results, with all discrepancies being additional antigens identified by molecular typing, filling in serological blanks. We can identify all common heterozygote combinations using this method.

Recognition of an HLA-DPw1 specific alloantiserum raised by planned immunization

This study reports identification of the first alloantiserum specific for a single HLA-DP allele and presents valuable technical information for the serological detection of the HLA-DP gene product. Serological detection of the HLA-DP gene products was undertaken by analyzing a large number of alloantisera against an HLA-DP characterized, monocyte depleted, B-lymphocyte reference panel. After absorption of contaminating DR antibodies, one alloantiserum (SOW) which had been raised by planned immunization, was shown to have a correlation coefficient of 0.91 with DPw1 as defined by primed lymphocytes. No association was seen with any other HLA-A,-B,-C,-D,-DR, or -DQ specificity in either population or family studies. The HLA-DP typing of the serum donor and immunizing recipient support the conclusion. Evidence is presented which suggests that expression of the DP molecule is not stable, at least as detected by conventional microcytotoxicity techniques.

Factors involved in decreased detection of class II histocompatibility antigens on blood mononuclear cells from transplanted patients receiving immunosuppressive drugs

Class II histocompatibility antigens were assessed by complement-dependent cytotoxicity on B enriched mononuclear cells and on purified monocytes isolated from the peripheral blood of renal patients before and after transplantation. After transplantation, a significant decrease of detection of DR alloantigens (cytotoxicity score before transplantation 3 +/- 0.1; after transplantation 0.95 +/- 0.1; p less than 0.001) was found. A similar defect was observed both on B enriched frozen cells and on purified monocytes isolated during the post-transplant period. Nevertheless, antigens could be adequately detected by a sensitive microabsorption method and by a procedure involving preincubation of mononuclear cells at 37 degrees C for 3 h followed by B cells enrichment by rosetting. The 37 degrees C induced reexpression could be inhibited by 10 micrograms/ml cycloheximide and by 50 microM monensin. No difference was found in the magnitude either of decreased expression or of temperature-induced reexpression between patients treated by CyS-Pred and those receiving Aza-Pred. It is concluded that transplanted recipients disclose a reversible defect of the expression of class II histocompatibility antigens probably related to perturbation of various steps of intracellular biosynthesis and traffic of these molecules.

An eight-year study of HLA typing proficiency in Eurotransplant

The main purpose of Eurotransplant, an international organ exchange organisation, is to maximize the survival time of transplanted organs through tissue typing and matching. Regular proficiency testings are necessary to assess the reproducibility and the reliability of the HLA typings performed by the individual typing centres. Two different protocols have been used: 1) since 1978, 35 samples of blood and donor spleen were used for cell exchanges (CE) and typed by all participating laboratories; 2) since 1977 samples of donor spleen have been shipped to the reference laboratory in Leiden for retyping (RD) resulting in over 2600 comparable HLA typings. The discrepancy rates of the HLA-A, B, C and DR specificities were analysed over the years. A large number of discrepancies was due to false negative assignments which led to assumed homozygosity at one or more HLA-loci. The recognition of HLA-DR has improved dramatically but with much variation per DR specificity. The concordancy rates for HLA-AB + DR have improved from 40% in 1981 to 91% for CE and 80% for RD typings in 1984. The reproducibility of DR typings in individual laboratories also has improved greatly but there is still considerable variation between the different laboratories.

Ten-year progress report of the International Cell Exchange

For the past 10 years, the International Cell Exchange has been a useful tool for testing rare and unusual HLA antigens and monitoring the progress in detection of recognized specificities. Of special interest are the antigens proposed in the 8th Workshop - 8w57, 8w58, 8w59, and 8w66. Marked improvement could be seen in the detection of 8w59 (29%) and 8w66 (31%). Possible new variants of the A9 and A10 complexes were tested in several exchanges. As shown by the increasing yearly average percentages of detection, laboratories are improving in their ability to type Aw23, Aw24, A25, A26, A29; Bw39, Bw41, Bw54, Bw55, Bw57, Bw58, Bw60 and Bw62. Over 90% of the laboratories are now able to detect Aw24; B5, B17, and B40, and A29 has attained the status of being well defined.

Improved detection of HLA-Cw5 and Cw7 by two colour fluorescence technique

Reactivity of two Cw5 and three Cw7 antisera was compared in the standard NIH and the Two Colour Fluorescence (TCF) techniques. Contrary to the NIH, the TCF method yielded strong positive reactions which enabled clear assignment of the Cw5 and Cw7 specificities. The TCF technique combines three factors that increase the sensitivity of serum reactions: 1. typing on B lymphocytes, 2. prolonged incubation and 3. staining of the lysed cells with ethidium bromide.