HLA epitopes - Empirically defined as conformational amino acids sequences of the HLA antigen and are likely to be part of the binding sites of anti-HLA antibodies.

Antibodies against HLA antigens are ubiquitous in the sera of transplant patients. Analysis of anti-HLA antibodies specificity has gone through a long history of development using assays like agglutination and lymphocytotoxicity, which utilize lymphocytes, and flow cytometry, which utilize multiplex beads coupled with single antigens. Hundreds of HLA antigens are identified to date, and the realization that antibody reactivity against the antigens is multispecific presented difficulties in accurately defining antibody specificity.

HLA Epitopes: The Targets of Monoclonal and Alloantibodies Defined.

Sensitization to human leukocyte antigens (HLA) in organ transplant patients causes graft rejection, according to the humoral theory of transplantation. Sensitization is almost ubiquitous as anti-HLA antibodies are found in almost all sera of transplant recipients. Advances in testing assays and amino acid sequencing of HLA along with computer software contributed further to the understanding of antibody-antigen reactivity.

Dynamics and epitope specificity of anti-human leukocyte antibodies following renal allograft nephrectomy.

Background: A considerable proportion of patients awaiting kidney transplantation is immunized by previous transplantation(s). We investigated how allograft nephrectomy (Nx) and withdrawal of maintenance immunosuppression (WD-MIS) in patients with a failed renal allograft contribute to allosensitization.

Methods: HLA antibodies (HLAabs) were analyzed before and after Nx and/or WD-MIS using a single antigen bead assay.

HLA class II DQA and DQB epitopes: recognition of the likely binding sites of HLA-DQ alloantibodies eluted from recombinant HLA-DQ single antigen cell lines.

Donor-specific antibodies (DSA) in sera of sensitized transplant patients are often produced against the specific epitopes on mismatched HLA antigens. In this study, we selected sera from 30 kidney transplant patients with DSA and AMR to define DQ epitopes. Using adsorption and elution assays, we identified 18 antibody reaction patterns to define 6 new epitopes and to confirm 12 previously defined epitopes.

Clinically irrelevant circulating human leukocyte antigen antibodies in the presence of ventricular assist devices.

Introduction: Identification of anti-human leukocyte antigen (HLA) antibodies by single-antigen beads (SAB) allows for prediction of donor-specific crossmatches (virtual crossmatches), thus facilitating the allocation of organs from deceased donors. However, the clinical relevance of HLA antibodies identified by SAB has been less than clear. This study demonstrates that sera from cardiac transplant candidates with a ventricular assist device (VAD) or infection may contain clinically irrelevant antibodies that bind to the beads but not to lymphocytes.

Effect of amino acid mismatch in the UNOS dataset.

This study began with the 2010 UNOS data-set of 181,653 deceased donor kidney transplant cases and 92,577 living donor cases. Cases with ambiguous or missing HLA typing were excluded, and the remaining cases were split into subgroups by the number of previous transplants and ethnic groups of donor-patient pairs. 41,128 Caucasian donor-patient pairs that were primary living-donor transplant cases were used as the pilot population to identify potential epitope groups that have a negative effect on graft outcome.

Anti-HLA-E mAb 3D12 mimics MEM-E/02 in binding to HLA-B and HLA-C alleles: Web-tools validate the immunogenic epitopes of HLA-E recognized by the antibodies.

HLA-E shares several peptide sequences with HLA-class Ia molecules. Therefore, anti-HLA-E antibodies that recognize the shared sequences may bind to HLA-class Ia alleles. This hypothesis was validated with a murine anti-HLA-E monoclonal antibody (mAb) MEM-E/02, which reacted with microbeads coated with several HLA-B and HLA-C antigens.

Antibodies to HLA-E in nonalloimmunized males: pattern of HLA-Ia reactivity of anti-HLA-E-positive sera.

Natural anti-HLA Abs found in sera of healthy nonalloimmunized males recognize HLA-Ia alleles parallel to those recognized by anti-HLA-E mAbs (MEM-E/02/06/07). Therefore, some of the HLA-Ia Abs seen in healthy males could be due to anti-HLA-E Abs cross-reacting with HLA-Ia. If anti-HLA-E Abs occur in healthy nonalloimmunized males, it can be assessed whether they evoke HLA-Ia reactivity as do mouse HLA-E mAbs.

New HLA class I epitopes defined by murine monoclonal antibodies.

This study defines 10 epitopes by murine monoclonal antibodies, of which seven are new and three were previously defined by alloantibodies. Of particular interest, three antibodies reacted with almost all Bw4-associated antigens except that each was negative with one or two of the antigens. One was negative with B13, one negative with A25, and another negative with B13 & A24 antigens.

HLA-E monoclonal antibodies recognize shared peptide sequences on classical HLA class Ia: relevance to human natural HLA antibodies.

The non-classical HLA-Ib molecule, HLA-E share several peptide sequence similarities with the heavy chains of classical HLA class Ia (-B and -C) molecules. Therefore, the antibodies to HLA-E, that recognize shared sequences, may bind to HLA-Ia alleles. This hypothesis is tested by examining the affinity of HLA-E monoclonal antibodies (HLA-E-MAbs) to HLA-Ia molecules and by inhibiting the antibody binding to both HLA-E and HLA-Ia with the shared peptide sequence(s).

Epitopes of human leukocyte antigen class I antibodies found in sera of normal healthy males and cord blood.

This study defines 96 epitopes targeted by human leukocyte antigen (HLA) antibodies reported in the sera of normal healthy males with no history of deliberate alloimmunizations and in cord blood. These epitopes are accessible for antibody binding on either the intact or the dissociated forms of recombinant HLA class I single antigens. Sixty percent of the epitopes are accessible on dissociated antigens, are defined mostly by hidden amino acids, and are designated as cryptic epitopes.

Epitopes of HLA-A, B, C, DR, DQ, DP and MICA antigens.

This chapter presents lists of HLA epitopes that have been defined to date. It also presents examples of reactions of mAb and eluted allosera with the class I, class II and MICAsingle antigen beads. To date, we have identified 110 class I epitopes, of which 47 were defined by mAbs and 63 by alloantibodies that were eluted from rHLA class I single antigen cell lines.

"Natural" human leukocyte antigen antibodies found in nonalloimmunized healthy males.

Background: Human leukocyte antigen (HLA) antibodies were normally not found in subjects who have not been immunized by pregnancies, transfusions, or transplants. But with new methodology, we now see that HLA antibodies are often found in nonalloimmunized males.

Methods: The sera of 424 healthy male donors were tested with single antigen Luminex beads.

Human leukocyte antigen class II DQ alpha and beta epitopes identified from sera of kidney allograft recipients.

Background: Epitopes are the sites to which antibodies bind. Both alpha and beta peptide chains of the human leukocyte antigen-DQ heterodimers (DQA1 and DQB1, respectively) contain polymorphic regions. We can identify DQA1 and DQB1 epitopes by DQ single antigen beads assay of the antibodies, correlating the beads' reaction patterns with either DQA1 or DQB1 alleles.

HLA class II DP epitopes.

Both alpha (DPA1) and beta (DPB1) peptide chains of class II HLA-DP heterodimers contain polymorphic regions. Five DPB1 epitopes, for which we propose numbers #4001-4005, were identified by the reaction patterns ofthe DPB1 antibodies to DPB1 alleles of DP single antigen beads. Epitopes were defined by unique amino acids shared by the positive antigens of theantibodies.

Epitopes of the HLA-A, B, C, DR, DQ and MICA antigens.

The intent for this chapter was to summarize the HLA epitopes that have been defined by adsorption and elution of antibodies from single HLA antigens to date. Examples of reactions of mAb and eluted allosera with the class I, class II and MICA SA are also presented. We have identified 103 HLA class I epitopes, of which 40 were defined by mAbs and 63 by alloantibodies mostly eluted from rHLA class I single antigen cell lines.

HLA class II DQ epitopes.

1. DQ epitopes were defined by studying the distinct reaction profiles of 17 allosera and 35 DQ-specific mouse monoclonal antibodies to HLA class II single antigen beads coated with purified recombinant DQ molecules. 2.

HLA class I epitopes: C-locus.

Here we identify 12 C antigen epitopes of which four are exclusively found on the C antigens, and inter-locus epitopes including five shared by B and C and three shared by A, B and C antigens.

HLA class I epitopes: A and B loci.

After our initial report on the HLA class I epitopes, we continue to demonstrate the power of the HLA recombinant single antigens in identifying the specificities of mouse monoclonal antibodies and alloantibodies that were absorbed to and eluted from single HLA antigens expressed by recombinant HLA single antigen cell lines (rHLA cell lines). We have expanded the list of HLA class I epitopes to 94, including the 58 reported earlier. Groups of as many as 58 HLA antigens can apparently share a single epitope.

Immunogenic HLA class I epitopes identified by humoral response to pregnancies.

The main objective of this study was to understand the humoral immunity against HLA so that this knowledge can be applied clinically. We investigated the various factors resulting in antibody production by 128 mothers against the child's inherited paternal alleles. Among 128 mother-child pairs, 39 different mismatch antigens were observed.

Epitopes of HLA antibodies found in sera of normal healthy males and cord blood.

This chapter defines epitopes targeted by antibodies in the sera of two populations of healthy normal males and in cord blood samples from a third population. These epitopes are accessible for antibody binding on either the intact or dissociated forms of recombinant HLA class I single antigens. Sixty percent of these epitopes are defined by hidden amino acids, and are therefore designated as cryptic epitopes.

Human leukocyte antigen class I epitopes: update to 103 total epitopes, including the C locus.

Background: Epitopes of human leukocyte antigen (HLA) are the sites to which the antibodies bind. We identify here 103 HLA class I epitopes shared by groups of class I antigens. In particular, our emphasis was on identifying epitopes exclusive to the C-locus antigens or interlocus epitopes among A, B, and C antigens.

HLA class I epitopes: recognition of binding sites by mAbs or eluted alloantibody confirmed with single recombinant antigens.

Development of beads coated with single recombinant HLA antigens has permitted the confirmation and further definition of HLA class I epitopes. In this study, monoclonal antibodies (mAbs) or alloantibodies eluted from recombinant cell lines were tested for reactivity with Luminex beads individually coated with 79 recombinant HLA class I single antigen (rHLA SA). Published amino acid sequences were used to map epitopes common to sets of antigens reactive with each antibody.

Analysis of HLA class I specific antibodies in patients with failed allografts.

Background: The goals of this study are first to determine the epitope specificity of donor specific antibody (DSA) in the serum of alloimmunized transplant patients with a failed renal graft; and second to understand the correlation between the development of DSA and nondonor specific antibody (NDSA).

Methods: The sera of 35 pretransplant panel reactive antibody (PRA)-negative patients with failed allografts were examined with single-antigen (SA) luminex beads to identify human leukocyte antigen (HLA)-A and -B antibodies. Potential HLA antibody epitopes were identified by using computer software and verified by absorption and elution from single-antigen cell lines.

Detection of antibodies to HLA-DP in renal transplant recipients using single antigen beads.

With the development of single DP-antigen beads, antibodies to DP could clearly be segregated from other HLA antibodies. We studied 323 sera of patients from four different centers with functioning or rejected kidney grafts. DP antibodies were found in 5.