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

Abstract

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.

Figure 1

Stimulation of a representative T cell line derived from the BAL of CBD patient 1. Proliferation of the T cell line to phytohemagglutinin (PHA) (5 μg/ml), BeSO₄ (1 × 10^-5 M), and Al₂(SO₄)₃ (1 × 10^-5 M) in the presence of autologous, irradiated PBMCs as antigen-presenting cells is shown. The data are presented as the mean cpm ± SEM.

Figure 2

Inhibition of the T cell proliferative responses to beryllium with mAbs to class II MHC molecules. T cell lines from CBD patient 1 were cultured with autologous LCL, 1 × 10^-6 M BeSO₄, and increasing concentrations of anti-class II mAb. Background proliferation without addition of BeSO₄ was 6,262 ± 122, and stimulation to BeSO₄ without inhibitory antibodies was 25,574 ± 739 cpm. The data are presented as percentage inhibition of stimulation as a function of the concentration of anti-class II mAbs.

Figure 3

Stimulation of the T cell line from CBD patient 2 with a fibroblast cell line (DP8302) transfected to express only HLA-DP (DPB1*0201 and DPA1*0103). Stimulation with BeSO₄ (1 × 10^-5 M) is shown on the left. Inhibition of this response with the addition of anti-DR or anti-DP mAb is shown on the right, and data are presented for both absolute cpm ± SEM and percent inhibition.

Figure 4

Determination of the class II MHC allele restriction of BeSO₄-specific T cell lines from (a) CBD patient 1 and (b) CBD patient 2. Stimulation of T cell lines was performed with autologous LCLs or allogeneic antigen-presenting cells in the presence of 1 × 10^-5 M or 1 × 10^-6 M BeSO₄. The stimulation index for each of the various presenting cells is shown over each bar, and the molecular typing of the DPB1 and DRB1 alleles for each antigen-presenting cell is shown on the right. Data are expressed as the mean cpm ± SEM.

Figure 5

Stimulation of the T cell line from CBD patient 2 using nonrestricting DPB1 alleles. In the presence of 1 × 10^-5 M BeSO₄, the T cell line from CBD patient 2 was stimulated with various antigen-presenting cells not matched for this individual's DP or DR alleles. Stimulation also was inhibited by the addition of 10 μg/ml of anti-DP mAb. The stimulation indices for each of the various conditions and the molecular typing of the DPB1 and DRB1 alleles for each antigen-presenting cell are shown. Data are expressed as the mean cpm ± SEM.

Figure 6

Modeling of the HLA-DP molecule based on the DR1 molecule. (a) Top view of the DR1 peptide-binding cleft, with a green α-chain and a cyan β-chain. (b) Side view of the DR1 peptide binding groove. The HA_306–318 peptide is indicated by pink sticks. The polymorphic charged residues at positions 55–56 and 69, indicated as red balls, are located in the peptide binding region. Despite the appearance from the ribbon structure, minimal, if any, portions of these polymorphic residues are exposed on the outside or top of the β-chain.