Defects of T-cell effector function and post-thymic maturation in X-linked hyper-IgM syndrome

Abstract

X-linked hyper-IgM syndrome (XHIM) results from mutations in the gene encoding for CD40 ligand (CD154). Patients with the syndrome suffer from infections with opportunistic pathogens such as Cryptosporidium and Pneumocystis carinii. In this study, we demonstrate that activated T cells from patients with XHIM produce markedly reduced levels of IFN-gamma, fail to induce antigen-presenting cells to synthesize IL-12, and induce greatly reduced levels of TNF-alpha. In addition, we show that the patients' circulating T lymphocytes of both the CD4(+) and CD8(+) subsets contain a markedly reduced antigen-primed population, as determined by CD45RO expression. Finally, we demonstrate that the defects in antigen priming are likely due to the lack of CD154 expression and insufficient costimulation of T cells by CD80/CD86 interactions. Taken together, this study offers a basis for the increased susceptibility of patients with XHIM to certain opportunistic infections.

Figures

Figure 1

Structure of the human CD40L gene, illustrating the nature and location of the mutations with respect to the extracellular, transmembrane, and intracellular regions (21). Numbering starts from A of the initiator (ATG) codon.

Figure 2

Secretion of IL-12 (pg/ml) obtained from patients with XHIM and from normal volunteers. PBMCs (2 × 106) were stimulated by anti-CD3ε, PHA/IFN-γ, LPS/IFN-γ, SAC/IFN-γ, or CD40L trimer/IFN-γ. Patient 6 was studied twice. Cytokine measurements were determined at 36 h by specific ELISA.

Figure 3

Secretion of TNF-α (pg/ml) obtained from patients with XHIM and from normal volunteers. PBMCs (2 × 106) were stimulated by anti-CD3ε, PHA/IFN-γ, LPS/IFN-γ, or SAC/IFN-γ. Cytokine measurements were determined at 36 h by specific ELISA.

Figure 4

Secretion of IFN-γ (pg/ml) obtained from patients with XHIM and from normal volunteers. PBMCs (2 × 106) were stimulated by anti-CD3ε, PHA, or anti-CD3ε/CD40L trimer. Cytokine measurements were determined at 36 h by specific ELISA.

Figure 5

Percentage of cells with exclusive expression of CD45RA or CD45RO in the CD4+ and CD8+ T-cell subsets of six patients with XHIM and from 40 controls. (a) Patients with XHIM have a marked reduction in the percentage of CD4+ T cells with expression of CD45RO (P < 0.0002) and an increase in the percentage of CD4+ T cells with expression of CD45RA (P < 0.0001). (b) Patients with XHIM also have a significant reduction in the percentage of CD8+ T cells with expression of CD45RO (P < 0.002) and an increase in CD8+ T cells expressing CD45RA (P < 0.0001).

Figure 6

Inhibition of CD28/B7 interaction blocks T-cell conversion from CD45RA+ to CD45RO+. PBMCs from a normal individual were depleted of CD45RO+-expressing cells. Cells were cultured at 106 cells/ml in media alone, or stimulated with SAC and control human IgG or SAC with CTLA4-Fc. Cells were harvested 60 h later and stained with anti-CD4 FITC and anti-CD45RO phycoerythrin, and two-color analysis was carried out using the same gate in all conditions. These data are representative of two normal donor samples.