title: Circulating memory B-cell subpopulations are affected differently by HIV infection and antiretroviral therapy.
abstract: OBJECTIVE
  To determine if the depletion of IgM memory B cells might contribute to the increased susceptibility of HIV patients to pneumococcal infection, memory B-cell subpopulations were investigated in HIV patients, including patients receiving antiretroviral therapy (ART).
  
  
  METHODS
  Blood B cells with the phenotype of IgM memory B cells (CD27, IgM) and switched memory B cells (CD27, IgM) were measured in antiretroviral-treated (n = 32) and untreated (n = 24) HIV patients and non-HIV controls (n = 35). Serum levels of IgG and IgG2 antibodies to pneumococcal polysaccharides, IgG, IgG subclasses, IgM and IgA were also assayed in HIV patients.
  
  
  RESULTS
  Switched memory B-cell counts were lower than controls in HIV patients (P < 0.01) irrespective of antiretroviral status and correlated with CD4 T-cell counts (r = 0.56, P = 0.001) in treated patients. In untreated patients, IgM memory B-cell counts correlated with CD4 T-cell counts (r = 0.73, P < 0.0001) reflecting higher values than controls in patients with CD4 T-cell counts greater than 300 cells/microl (P = 0.004) and lower values than controls in patients with CD4 T-cell counts below 300 cells/microl (P = 0.0001). There was no relationship between serum levels of pneumococcal antibodies and IgM or switched memory B cells.
  
  
  CONCLUSIONS
  The depletion of IgM memory B cells in untreated HIV patients with a CD4 T-cell count below 300 cells/microl might be a risk factor for pneumococcal infection. The depletion of switched memory B cells is a complication of HIV infection irrespective of ART and might contribute to impaired IgG antibody responses. Memory B-cell subpopulations might predict the risk of pneumococcal sepsis more accurately than the CD4 T-cell count or pneumococcal antibody levels.
authors: Department of Clinical Immunology and Immunogenetics, Royal Perth Hospital, Perth, WA 6847, Australia.
authors: Lloyd J
authors: LJ
authors: D'Orsogna
authors: Rom G
authors: RG
authors: Krueger
authors: Elizabeth J
authors: EJ
authors: McKinnon
authors: Martyn A
authors: MA
authors: French
mesh_terms: D017088:AIDS-Related Opportunistic Infections / Q000276:immunology; D000328:Adult; D019380:Anti-HIV Agents / Q000627:therapeutic use*; D000907:Antibodies, Bacterial / Q000097:blood; D016175:B-Lymphocyte Subsets / Q000187:drug effects / Q000276:immunology*; D018791:CD4 Lymphocyte Count; D003430:Cross-Sectional Studies; D005260:Female; D015658:HIV Infections / Q000188:drug therapy / Q000276:immunology*; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D007075:Immunoglobulin M / Q000097:blood; D007156:Immunologic Memory; D008297:Male; D008875:Middle Aged; D011008:Pneumococcal Infections / Q000276:immunology; D012367:RNA, Viral / Q000097:blood; D013296:Streptococcus pneumoniae / Q000276:immunology
chemical_list: D019380:Anti-HIV Agents; D000907:Antibodies, Bacterial; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D012367:RNA, Viral