B Cells and Programmed Death-Ligand 2 Signaling Are Required for Maximal Interferon-γ Recall Response by Splenic CD4⁺ Memory T Cells of Mice Vaccinated with Mycobacterium tuberculosis Ag85B

PLoS One. 2015 Sep 17;10(9):e0137783. doi: 10.1371/journal.pone.0137783. eCollection 2015.

Abstract

CD4+ T cells producing interferon-γ are crucial for protection against Mycobacterium tuberculosis infection and are the cornerstone of tuberculosis vaccination and immunological diagnostic assays. Since emerging evidence indicates that B cells can modulate T cell responses to M. tuberculosis infection, we investigated the contribution of B cells in regulating interferon-γ recall response by memory Thelper1 cells specific for Ag85B, a leading candidate for tuberculosis sub-unit vaccines. We found that B cells were able to maximize the reactivation of CD4+ memory T cells and the interferon-γ response against ex vivo antigen recall in spleens of mice vaccinated with Ag85B. B cell-mediated increase of interferon-γ response was particular evident for high interferon-γ producer CD4+ memory T cells, likely because those T cells were required for triggering and amplification of B cell activation. A positive-feedback loop of mutual activation between B cells, not necessarily antigen-experienced but with integral phosphatidylinositol-3 kinase (PI3K) pathway and a peculiar interferon-γ-producing CD4highT cell subset was established. Programed death-ligand 2 (PD-L2), expressed both on B and the highly activated CD4high T cells, contributed to the increase of interferon-γ recall response through a PD1-independent pathway. In B cell-deficient mice, interferon-γ production and activation of Ag85B-specific CD4+ T cells were blunted against ex vivo antigen recall but these responses could be restored by adding B cells. On the other hand, B cells appeared to down-regulate interleukin-22 recall response. Our data point out that nature of antigen presenting cells determines quality and size of T cell cytokine recall responses. Thus, antigen presenting cells, including B cells, deserve to be considered for a better prediction of cytokine responses by peripheral memory T cells specific for M. tuberculosis antigens. We also invite to consider B cells, PD-L2 and PI3K as potential targets for therapeutic modulation of T cell cytokine responses for tuberculosis control.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acyltransferases / immunology*
  • Animals
  • Antigens, Bacterial / immunology*
  • B-Lymphocytes / immunology*
  • Bacterial Proteins / immunology*
  • Cell Proliferation
  • Cells, Cultured
  • Cytokines / immunology
  • Female
  • Immunologic Memory / immunology
  • Interferon-gamma / immunology*
  • Interleukin-22
  • Interleukins / immunology
  • Lymphocyte Activation / immunology
  • Mice
  • Mice, Inbred C57BL
  • Mycobacterium tuberculosis / immunology*
  • Phosphatidylinositol 3-Kinase / metabolism
  • Programmed Cell Death 1 Ligand 2 Protein / immunology*
  • Programmed Cell Death 1 Receptor / metabolism
  • Signal Transduction / immunology
  • Th1 Cells / immunology*
  • Tuberculosis Vaccines / immunology
  • Vaccination
  • Vaccines, Subunit / immunology

Substances

  • Antigens, Bacterial
  • Bacterial Proteins
  • Cytokines
  • Interleukins
  • Pdcd1lg2 protein, mouse
  • Programmed Cell Death 1 Ligand 2 Protein
  • Programmed Cell Death 1 Receptor
  • Tuberculosis Vaccines
  • Vaccines, Subunit
  • Interferon-gamma
  • Acyltransferases
  • antigen 85B, Mycobacterium tuberculosis
  • Phosphatidylinositol 3-Kinase

Grants and funding

This work was supported by the Ministero della Salute (IT) 3H/16.