Variable presence of circulating cytokines in patients with sporadic or X-linked lymphoproliferative disease with fatal infectious mononucleosis

Increased lymphocyte viability after non-stimulated peripheral blood mononuclear cell (PBMC) culture in patients with X-linked lymphoproliferative disease (XLP)

Survival of lymphocytes after prolonged culture was studied in two asymptomatic XLP patients. Viability of XLP PBMC after 30 days of non-stimulated culture was higher than that of normal controls (N), mainly due to the persistence of CD8 memory lymphocytes. IFNgamma high CD8 T lymphocytes remained higher in XLP than in N after 30 days. The number of perforin+ CD8 lymphocytes was markedly reduced after 30 days in XLP and in N. Increased viability was not related to CD127, PD-1, CD27, or CD62L expression. Concerning B lymphocytes, memory CD27+ CD19+ cells prevailed over CD27- cells after 30 days in both XLP and N, with far more surviving cells in XLP. In N, few CD19+ B lymphocytes were viable after prolonged culture. In XLP, these cells were also IgD+, IgM+ and EBNA2+. These results demonstrate that IFNgamma-positive memory CD8 T cells persist in XLP after prolonged culture in association with a subset of viable memory CD27+ B cells expressing latent EBV antigens. The survival advantage of XLP cells might be related to increased frequency of extranodal lymphoma in XLP patients.

Regulation of cellular and humoral immune responses by the SLAM and SAP families of molecules

SAP (SLAM-associated protein) was identified in 1998 as an adaptor molecule involved in the intracellular signaling pathways elicited through the cell surface receptor SLAM and as the protein defective in the human immunodeficiency X-linked lymphoproliferative disease (XLP). During the past eight years, it has been established that the SLAM family of cell surface receptors (SLAM, 2B4, NTB-A, Ly9, CD84) and the SAP family of adaptors (SAP, EAT-2, ERT) play critical roles in lymphocyte development, differentiation, and acquisition of effector functions. Studies of these proteins have shown unexpected roles in cytokine production by T cells and myeloid cells, T cell-dependent humoral immune responses, NK cell-mediated cytotoxicity, and NKT cell development. This review highlights recent findings that have improved our understanding of the roles of the SLAM and SAP families of molecules in immune regulation and discusses how perturbations in the signaling pathways involving these proteins can result in different disease states.

Loss of circulating CD27+ memory B cells and CCR4+ T cells occurring in association with elevated EBV loads in XLP patients surviving primary EBV infection

Detailed longitudinal studies of patients with X-linked lymphoproliferative disease (XLP) may increase our understanding of the immunologic defects that contribute to the development of lymphoma and hypogammaglobulinemia in XLP. We describe progressive changes observed in immunoglobulin concentrations, lymphocyte subsets, and Epstein-Barr virus (EBV) loads occurring in a 2-year period in a newly infected, but otherwise healthy, carrier (patient 9). We compare these findings with those observed in the patient's brother, who had hypogammaglobulinemia and XLP (patient 4). Immunoglobulin G (IgG), IgM, and IgA concentrations increased in patient 9 during acute EBV infection, but thereafter they decreased steadily to concentrations consistent with hypogammaglobulinemia, reaching a plateau 5 months after infection. In both patients, CD19+ B-lymphocyte rates remained lower than 3%, with a contraction of the B-cell memory compartment (CD27+ CD19+/CD19+) to 20% (normal range, 32%-56%). T-lymphocyte subpopulations showed a reduction in CD4+ T-cell counts and a permanent CD8+ T-cell expansion. Interestingly, CXCR3 memory TH1 cells were expanded and CCR4+ TH2 lymphocytes were reduced, suggesting that abnormal skewing of memory T-cell subsets might contribute to reduced antibody synthesis. Despite an expanded number of CD3+CD8+ lymphocytes, increased EBV loads occurred in both patients without overt clinical symptoms of mononucleosis, lymphoproliferative disease, or lymphoma.

Haematological associations of Epstein-Barr virus infection

Epstein-Barr virus (EBV) is one of eight human herpesviruses and is ubiquitous. Primary infection with EBV in childhood is generally silent, but often causes overt diseases such as infectious mononucleosis (IM) and lymphoproliferative disorders (LPD). The latter occurs in immunologically compromised individuals. Historically, EBV has been thought to be aetiologically linked to human malignancies such as EBV genome-positive Burkitt's lymphoma (BL) and nasopharyngeal carcinoma (NPC). Furthermore, studies using recent developments in molecular and immunological diagnostic approaches have suggested that this virus has a causative role in a spectrum of human diseases of previously unknown pathogenesis, including chronic active EBV infection syndrome (CAEBV), EBV-related haemophagocytic lymphohistiocytosis (HLH), and certain disorders such as EBV genome-positive T-cell lymphoma, natural killer (NK) cell leukaemia/lymphoma, Hodgkin's disease (HD) and gastric carcinoma. This chapter reviews recent progress regarding EBV-associated diseases.

Epstein-Barr virus-associated hemophagocytic syndrome and fatal infectious mononucleosis

Virus-associated hemophagocytic syndrome (VAHS) has been thought to be a distinct clinical entity, characterized by intermittent fever, enlarged liver and spleen, and the appearance of hemophagocytosis. Hemopoietic cells are actively ingested by monocytes/macrophages in various organs, including lymph nodes, bone marrow, liver, and spleen. Epstein-Barr virus (EBV) is now thought to be one of the major causes for the development of this unique syndrome. Additionally, VAHS is often associated with fatal infectious mononucleosis (IM). The relationship between EBV-associated VAHS and fatal IM is discussed in this concise review.