Mycobacterium tuberculosis lung infection results in a complex multicellular structure: the granuloma. In some granulomas, immune activity promotes bacterial clearance, but in others, bacteria persist and grow. We identified correlates of bacterial control in cynomolgus macaque lung granulomas by co-registering longitudinal positron emission tomography and computed tomography imaging, single-cell RNA sequencing, and measures of bacterial clearance. Bacterial persistence occurred in granulomas enriched for mast, endothelial, fibroblast, and plasma cells, signaling amongst themselves via type 2 immunity and wound-healing pathways. Granulomas that drove bacterial control were characterized by cellular ecosystems enriched for type 1-type 17, stem-like, and cytotoxic T cells engaged in pro-inflammatory signaling networks involving diverse cell populations. Granulomas that arose later in infection displayed functional characteristics of restrictive granulomas and were more capable of killing Mtb. Our results define the complex multicellular ecosystems underlying (lack of) granuloma resolution and highlight host immune targets that can be leveraged to develop new vaccine and therapeutic strategies for TB.
Copyright © 2022 The Author(s). Published by Elsevier Inc. All rights reserved.

Chediak-Higashi syndrome (CHS) is caused by autosomal recessive mutations in LYST, resulting in enlarged lysosomal compartments in multiple cell types. CHS patients display oculocutaneous albinism and may develop life-threatening hemophagocytic lymphohistiocytosis (HLH). While NK cell-mediated cytotoxicity has been reported to be uniformly defective, variable defects in T cell-mediated cytotoxicity has been observed. The latter has been linked to the degree of HLH susceptibility. Since the discrepancies in NK cell- and T cell-mediated cellular cytotoxicity might result from differences in regulation of cytotoxic granule release, we here evaluated perforin-containing secretory lysosome size and number in freshly isolated lymphocytes from CHS patients and furthermore compared their exocytic capacities. Whereas NK cells from CHS patients generally contained a single, gigantic perforin-containing granule, cytotoxic T cells predominantly contained several smaller granules. Nonetheless, in a cohort of 21 CHS patients, cytotoxic T cell and NK cell granule exocytosis were similarly impaired upon activating receptor stimulation. Mechanistically, polarization of cytotoxic granules was defective in cytotoxic lymphocytes from CHS patients, with EEA1, a marker of early endosomes, mislocalizing to lysosomal structures. The results leads to the conclusion that lysosome enlargement corresponds to loss of distinct organelle identity in the endocytic pathway, which on a subcellular level more adversely affects NK cells than T cells. Hence, vesicular size or numbers do not per se dictate the impairment of lysosomal exocytosis in the two cell types studied.

Psoriasis is a chronic inflammatory disease that affects the skin. CD4(+) CD28(null) cells are a subset of T lymphocytes associated with systemic inflammation and increased cardiovascular disease risk, and may be involved in the pathogenesis of psoriasis.
To study the features of circulating CD4(+) CD28(null) cells in patients with psoriasis, adjusted for the influence of known cardiovascular disease risk factors.
Forty-two patients with psoriasis and 42 controls entered the study. Peripheral blood mononuclear cells were analysed for the frequency of CD4(+) CD28(null) T lymphocytes and their expression of cytotoxic granules and homing receptors. Immunostaining for cutaneous cytotoxic granules was assessed in skin biopsies from 11 patients.
There were no differences in the frequency of CD4(+) CD28(null) T cells between groups in all situations analysed. However, there was an increased number of cells expressing cytotoxic granules and a decreased number expressing CXCR3 in ex vivo samples of patients with psoriasis. A negative correlation was observed between the frequency of ex vivo CD4(+) CD28(null) cells and psoriasis severity. After clinical remission in nine patients, ex vivo CD4(+) CD28(null) lymphocytes expressing cytotoxic granules decreased. Perforin-, granzyme B- and granulysin-containing cells were found in skin lesions. Patients with psoriasis also had increased plasma levels of C-reactive protein.
These data suggest that cytotoxic cells, such as CD4(+) CD28(null) lymphocytes, within an inflammatory environment may play a role in the pathogenesis of psoriasis.
© 2015 British Association of Dermatologists.

Interleukin-21 (IL-21) is a cytokine with pleiotropic effects on various cell types including dendritic cells, B cells, T cells and natural killer (NK) cells. To evaluate if IL-21 affects human NK cell subpopulations in a similar fashion, functional studies were performed on CD56(dim) and CD56(bright) NK cells, both bearing IL-21 receptors at identical densities. Stimulation with IL-21 strongly induced proliferation of CD56(bright) NK cells and cytotoxicity against K562 target cells was preferentially augmented in CD56(dim) NK cells. In contrast, stimulation with IL-2 and IL-21 alone or in combination failed to induce interferon-gamma and tumour necrosis factor-alpha production in the two NK cell subsets. Intracellular analysis of signal transducer and activator of transcription (STAT) proteins revealed that IL-21 by itself induces phosphorylation of STAT1 and STAT3 in CD56(dim) NK cells, and to an even higher degree in CD56(bright) NK cells. In this CD56(bright) NK cell population alone, IL-2 weakly phosphorylated STAT1 and STAT3, which was further increased when cells were treated with the combination of both cytokines. In contrast, STAT5 was strongly phosphorylated only in CD56(bright) NK cells by low-dose IL-2, while IL-21 did not affect STAT5 at all. In summary, we present data indicating that the NK-cell-directed cytokines IL-2 and IL-21 not only affect functions in NK cell subpopulations differently but can also act additively.

Protective immunity in tuberculosis is dependent on the coordinated release of cytolytic effector molecules from effector T cells and the subsequent granule-associated killing of infected target cells. In this study, we investigated the expression of cytolytic (perforin and granzyme A) and antimicrobial (granulysin) molecules at the single-cell level in cryopreserved lung tissue from patients with chronic, progressive tuberculosis disease. Quantification of protein-expressing cells was performed by in situ imaging, while mRNA levels in the infected tissue were analyzed by real-time PCR. Persistent inflammation, including excessive expression of inducible nitric oxide synthase in CD68+ macrophages and significant infiltration of CD3+, CD8+ and CD4+ T cells, was evident in tuberculosis lesions in all patients. However, despite the accumulation of CD3+ T cells, perforin- and granulysin-expressing CD3+ T cells were detected at two- to threefold-lower ratios in the tuberculosis lesions than in distal lung parenchyma and uninfected control lungs, respectively. This was evident at both the protein and mRNA levels. Moreover, perforin- and granulysin-expressing CD8+ T cells were scarce in individual granulomas within the tuberculosis lesions. In contrast, significant up-regulation of granzyme A-expressing CD3+ T cells was evident in the lesions from all patients. Confocal microscopy revealed coexpression of perforin and granulysin, primarily in CD8+ T cells; however, this expression was lower in the tuberculosis lesions. These findings suggest that symptomatic, chronic tuberculosis disease is associated with insufficient up-regulation of perforin and granulysin coexpression in CD8+ T cells at the local site of infection.