Myeloid and T Cell-Derived TNF Protects against Central Nervous System Tuberculosis

Abstract

Tuberculosis of the central nervous system (CNS-TB) is a devastating complication of tuberculosis, and tumor necrosis factor (TNF) is crucial for innate immunity and controlling the infection. TNF is produced by many cell types upon activation, in particularly the myeloid and T cells during neuroinflammation. Here we used mice with TNF ablation targeted to myeloid and T cell (MT-TNF^-/-) to assess the contribution of myeloid and T cell-derived TNF in immune responses during CNS-TB. These mice exhibited impaired innate immunity and high susceptibility to cerebral Mycobacterium tuberculosis infection, a similar phenotype to complete TNF-deficient mice. Further, MT-TNF^-/- mice were not able to control T cell responses and cytokine/chemokine production. Thus, our data suggested that collective TNF production by both myeloid and T cells are required to provide overall protective immunity against CNS-TB infection.

Keywords: CNS; Mycobacterium tuberculosis; T cell; myeloid; tumor necrosis factor.

Figure 1

Tumor necrosis factor (TNF) produced by myeloid and T-cells is essential for protection against Mycobacterium tuberculosis infection in the brain. TNF^f/f (black circle), MT-TNF^−/− (black square) and TNF^−/− (clear circle) mice were infected with M. tuberculosis H37Rv at a dose of 1 × 10⁴–1 × 10⁵ CFU/brain by intracerebral inoculation. Mortality (A) and body weight changes (B) were measured and recorded for the experimental duration (n = 5–7 mice/group). (C) Bacterial burdens in brains, spleens, and lungs were determined at day 14 and 21 postinfection. These data were one representative out of three to five independent experiments (*p ≤ 0.05, **p ≤ 0.01, and ***p ≤ 0.001).

Figure 2

Myeloid cells and T-cells are important source for tumor necrosis factor (TNF)-dependent pathology during cerebral tuberculosis. Hematoxylin and eosin-stained coronal brain sections of TNF^f/f, MT-TNF^−/−, and TNF^−/− mice (n = 5 mice/group) at day 21 postinfection are presented. Ventriculitis of the choroid plexus accompanied by necrosis (box) are observed. Corresponding Ziehl–Neelsen stain revealed acid-fast bacilli (arrows). The images are representatives of three to five independent experiments.

Figure 3

Tumor necrosis factor (TNF) production by myeloid cells and T-cells is required for activation and regulation of innate immunity during cerebral tuberculosis. TNF^f/f (black), MT-TNF^−/− (gray), and TNF^−/− (clear) mice were infected with Mycobacterium tuberculosis H37Rv at a dose of 1 × 10⁴–1 × 10⁵ CFU/brain by intracerebral inoculation. The number of (A) CD11b⁺CD45^low microglia and (B) CD11b⁺CD45^high macrophages and the frequency of (C,D) MHC II and (E,F) CD80 expression was analyzed by flow cytometry at day 21 postinfection. Data (mean ± SEM of five mice) are representative of three repeat experiments (*p ≤ 0.05, **p ≤ 0.01, and ***p ≤ 0.001).

Figure 4

Cerebral tuberculosis-induced T-cell response is dependent on the myeloid and T-cells-derived tumor necrosis factor (TNF). (A) Representative FACS plots of CD3⁺CD4⁺ and CD3⁺CD8⁺ cells in TNF^f/f, MT-TNF^−/−, and TNF^−/− mice at day 21 after intracerebrally infected with Mycobacterium tuberculosis H37Rv. The number of (B) CD3⁺CD4⁺ and (C) CD3⁺CD8⁺, and the frequency of (D) CD4⁺CD44⁺ and (E) CD8⁺CD44⁺ expression, was analyzed by flow cytometry at day 21 postinfection. Data (mean ± SEM of five mice) are representative of three repeat experiments (*p ≤ 0.05, **p ≤ 0.01, and ***p ≤ 0.001).

Figure 5

Myeloid and T-cells-derived tumor necrosis factor (TNF) regulates synthesis of cytokine and chemokines. (A) TNF, (B) IFN-γ, (C) IL-2, (D) IL-6, (E) IL-12p70, (F) MIP-1α, (G) MCP-1, and (H) RANTES cerebral concentrations were measured by ELISA in TNF^f/f, MT-TNF^−/−, and TNF^−/− mice at day 21 after intracerebrally infected with Mycobacterium tuberculosis H37Rv. Data (mean ± SEM of five mice) are representative of at least three repeat experiments (*p ≤ 0.05, **p ≤ 0.01, and ***p ≤ 0.001).