HLA-DP--part of the concert

Differences in Expression of Human Leukocyte Antigen Class II Subtypes and T Cell Subsets in Behçet's Disease with Arthritis

It has been reported Human Leukocyte Antigen (HLA) gene polymorphism is a risk factor for the development of Behçet’s disease (BD). In this study, the association of HLA class II subtypes HLA-DP, DQ, DR, and T cell subsets in BD patients with arthritis was evaluated. Frequencies of HLA-DP, DQ, DR positive cells, and T cell subsets in peripheral blood leukocytes (PBL) were measured by flow cytometric analysis in BD, and compared to rheumatoid arthritis as disease controls and healthy controls. Frequencies of HLA-DQ were significantly decreased in whole PBL and granulocytes of BD active patients as compared to healthy controls. In monocytes populations, proportions of HLA-DR positive cells were significantly increased in BD active patients as compared to healthy controls. Proportions of CD4+CCR7+ and CD8+CCR7+ cells were significantly higher in BD active patients than in BD inactive in whole PBL. Frequencies of CD4+CD62L- and CD8+CD62L- cells in lymphocytes were significantly decreased in active BD than those in inactive BD. There were also correlations between disease activity markers and T cell subsets. Our results revealed HLA-DP, DQ, and DR expressing cell frequencies and several T cell subsets were significantly correlated with BD arthritis symptoms.

Strategies to Reduce the Immunogenicity of Recombinant Immunotoxins

Recombinant immunotoxins (RITs) are genetically engineered proteins being developed to treat cancer. They are composed of an Fv that targets a cancer antigen and a fragment of a bacterial toxin that kills tumor cells. Because the toxin is a foreign protein, it is immunogenic. The clinical success of RITs in patients with a normal immune system is limited by their immunogenicity. In this review, we discuss our progress in therapeutic protein deimmunization and the balancing act between immunogenicity and therapeutic potency. One approach is to prevent the activation of B cells by mapping and elimination of B-cell epitopes. A second approach is to prevent helper T-cell activation by interfering with major histocompatibility complex II presentation or T-cell recognition. Immunizing mice with RITs that were deimmunized by elimination of the murine B- or T-cell epitopes showed that both approaches are effective. Another approach to control immunogenicity is to modify the host immune system. Nanoparticles containing synthetic vaccine particles encapsulating rapamycin can induce immune tolerance and prevent anti-drug antibody formation. This treatment restores RIT anti-tumor activity that is otherwise neutralized because of immunogenicity.

HLA-DP in unrelated hematopoietic cell transplantation revisited: challenges and opportunities

When considering HLA-matched hematopoietic cell transplantation (HCT), sibling and unrelated donors (UDs) are biologically different because UD-HCT is typically performed across HLA-DP disparities absent in sibling HCT. Mismatched HLA-DP is targeted by direct alloreactive T cell responses with important implications for graft-versus-host disease and graft-versus-leukemia. This concise review details special features of HLA-DP as model antigens for clinically permissive mismatches mediating limited T-cell alloreactivity with minimal toxicity, and describes future avenues for their exploitation in cellular immunotherapy of malignant blood disorders.

Role of HLA-DP in the Presentation of Epitopes from the Truncated Bacterial PE38 Immunotoxin

Identification of helper T-cell epitopes is important in many fields of medicine. We previously used an experimental approach to identify T-cell epitopes in PE38, a truncated bacterial toxin used in immunotoxins. Here, we evaluated the ability of antibodies to DR, DP, or DQ to block T-cell responses to PE38 epitopes in 36 PBMC samples. We predicted the binding affinities of peptides to DR, DP, and DQ alleles using computational tools and analyzed their ability to predict the T-cell epitopes. We found that HLA-DR is responsible for 65% of the responses, DP 24%, and DQ 4%. One epitope that is presented in 20% of the samples (10/50) is entirely DP restricted and was not predicted to bind to DR or DP reference alleles using binding algorithms. We conclude that DP has an important role in helper T-cell response to PE38.

DPB1*8601, a previously unrecognized DPB1 variant in the Caucasoid population

A new, previously unrecognized DPB1* allele, DPB1*8601, was found in a Swedish family. The new allele was carried on the common North European haplotype HLA A1-B8-DR3. Both individuals carrying the new allele were initially typed as clear DPB1*4601,*6601 but after family studies and further typing with allele-specific primers it was concluded that a new allele was present together with the common DPB1*0401. The new allele was investigated by direct sequencing of exon 2 in both forward and reverse directions employing intron primers combined with either an allele-specific sense or anti-sense biotinylated primer for bi-directional sequencing. The new allele is identical to DPB1*1701 in the five first variable regions. In the sixth region, however, DPB1*8601 carries the GGPM motif shared by several common alleles such as DPB1*0201 and 0401and 0402.

Beryllium presentation to CD4+ T cells underlies disease-susceptibility HLA-DP alleles in chronic beryllium disease

Chronic beryllium disease results from beryllium exposure in the workplace and is characterized by CD4(+) T cell-mediated inflammation in the lung. Susceptibility to this disease is associated with particular HLA-DP alleles. We isolated beryllium-specific T cell lines from the lungs of affected patients. These CD4(+) T cell lines specifically responded to beryllium in culture in the presence of antigen-presenting cells that expressed class II MHC molecules HLA-DR, -DQ, and -DP. The response to beryllium was nearly completely and selectively blocked by mAb to HLA-DP. Additional studies showed that only certain HLA-DP alleles allowed presentation of beryllium. Overall, the DP alleles that presented beryllium to disease-specific T cell lines match those implicated in disease susceptibility, providing a mechanism for this association. Based on amino acid residues shared by these restricting and susceptibility DP alleles, our results provide insight into the residues of the DP beta-chain required for beryllium presentation.

T-Cell epitopes and human leukocyte antigen restriction elements of an immunodominant antigen of Blastomyces dermatitidis

Humans infected with the dimorphic fungus Blastomyces dermatitidis develop strong T-lymphocyte responses to WI-1, an immunodominant antigen that has been shown to elicit protective immunity in mice. In the present study, the T-cell epitopes of WI-1 and human leukocyte antigen (HLA) restricting elements that display them were investigated. Peripheral blood mononuclear cells (PBMC) from 37 patients with a confirmed history of blastomycosis were tested for a response to WI-1 in primary proliferation assays; PBMC from 35 (95%) responded. Six patients whose PBMC proliferated strongly in response to WI-1 (defined as a stimulation index greater than 50) were tested further for responses to subcloned, recombinant fragments of the antigen. These patients responded chiefly to sequences within the N terminus and the 25-amino-acid tandem repeat. Cloned CD4(+) T cells from an infected individual were used to delineate more precisely the peptide epitopes in the fragments and HLA restricting elements that present them. A majority of the T-cell clones recognized an epitope spanning amino acids 149 to 172 within the N terminus, displayed by HLA-DR 15. A minority of the clones, which have been shown to perform a cytolytic function in vitro, recognized an epitope in the tandem repeat displayed by HLA-DPw4, an uncommon restricting element. Tandem repeat epitopes required display by the beta chain of DPw4 heterodimers. Thus, human T cells with different functions in vitro also recognize distinct regions of WI-1, raising the possibility that HLA restricting elements that present them could modulate immunity during blastomycosis by selection and display of WI-1 peptides.

HLA DPA1/DPB1 genotype and haplotype frequencies, and linkage disequilibria in Nigeria, Liberia, and Gabon

The frequencies of DPA1 and DPB1 alleles and their occurrence in haplotypic linkage were assessed and compared in Nigerian, Liberian, and Gabonese individuals. Differences were seen in the distribution patterns; these differences were more pronounced between the Gabonese and the other two populations than between Liberians and Nigerians. Several haplotypic DPA1-DPB1 combinations could be verified by homozygosity. Linkage disequilibria of DPA1-DPB1 combinations, indicating further probable haplotypes, were estimated. Although different allele and haplotype frequencies were recognized in the three subgroups, the linkage disequilibria were mostly either positive or negative in all populations.