Granulysin-Expressing CD4+ T Cells as Candidate Immune Marker for Tuberculosis during Childhood and Adolescence

Abstract

BackgroundGranulysin produced by cytolytic T cells directly contributes to immune defense against tuberculosis (TB). We investigated granulysin as a candidate immune marker for childhood and adolescent TB.MethodsPeripheral blood mononuclear cells (PBMC) from children and adolescents (1–17 years) with active TB, latent TB infection (LTBI), nontuberculous mycobacteria (NTM) infection and from uninfected controls were isolated and restimulated in a 7-day restimulation assay. Intracellular staining was then performed to analyze antigen-specific induction of activation markers and cytotoxic proteins, notably, granulysin in CD4+ CD45RO+ memory T cells.ResultsCD4+ CD45RO+ T cells co-expressing granulysin with specificity for Mycobacterium tuberculosis (Mtb) were present in high frequency in TB-experienced children and adolescents. Proliferating memory T cells (CFSElowCD4+CD45RO+) were identified as main source of granulysin and these cells expressed both central and effector memory phenotype. PBMC from study participants after TB drug therapy revealed that granulysin-expressing CD4+ T cells are long-lived, and express several activation and cytotoxicity markers with a proportion of cells being interferon-gamma-positive. In addition, granulysin-expressing T cell lines showed cytolytic activity against Mtb-infected target cells.ConclusionsOur data suggest granulysin expression by CD4+ memory T cells as candidate immune marker for TB infection, notably, in childhood and adolescence.

TB or Not TB: That Is No Longer the Question

“…Because CD8 + effector memory T cells that produce granulysin also express surface TNF-a, they are depleted by anti-TNF-a immunotherapy for autoimmune diseases, which may contribute to reactivation of TB in these individuals (109). Granulysin has also been detected in CD4 + T cells (110), and its expression in CD4 + T cells has been suggested as a marker of TB in children (111). Adults with active TB have been shown to have significantly lower circulating granulysin in their plasma compared to healthy controls.…”

CD4+ T Cells Contain Early Extrapulmonary Tuberculosis (TB) Dissemination and Rapid TB Progression and Sustain Multieffector Functions of CD8+ T and CD3− Lymphocytes: Mechanisms of CD4+ T Cell Immunity

“…While multifunctional CD4+ T cells simultaneously producing IFN-γ/TNFα/IL-2 are detectable in Mtb infection (24, 25), CD4+ T cells can also function as cytotoxic cells and produce anti-Mtb perforin and granulysin in vitro . Murine CD4+ T cells can directly kill Mtb-infected cells in vivo , although the mechanism remain unclear (26, 27). The role of IL-17- and IL-22-producing CD4+ T cells has been investigated in animal models and whether these cells are protective or detrimental needs to be further investigated(28–30).…”

Granzyme A as a potential biomarker of Mycobacterium tuberculosis infection and disease

“…This improved mechanism of protection has also been demonstrated using antibody blockage of the granule exocytosis pathway, that dramatically reduced the lytic activity of T cells against Mtb-infected macrophages and the increase of intracellular growth of bacteria [28]. Similarly, granulysin expression by CD4 + memory T cells is a candidate immune marker for TB infection, notably, in childhood and adolescence [29] and CD4T cells expressing granulysin correlate with the clinical forms of leprosy [30]. Our own previous studies demonstrated significantly lower plasma granulysin levels in adults with active disease in highly endemic area in Indonesia, and in children with TB disease in Italy [31], which increased after completion of therapy.…”