Altered innate immune profile in blood of systemic mastocytosis patients

Abstract

Background Mast cells (MC) from systemic mastocytosis (SM) patients release MC mediators that lead to an altered microenvironment with potential consequences on innate immune cells, such as monocytes and dendritic cells (DC). Here we investigated the distribution and functional behaviour of different populations of blood monocytes and DC among distinct diagnostic subtypes of SM. Methods Overall, we studied 115 SM patients ‐ 45 bone marrow mastocytosis (BMM), 61 indolent SM (ISM), 9 aggressive SM (ASM)‐ and 32 healthy donors (HD). Spontaneous and in vitro‐stimulated cytokine production by blood monocytes, and their plasma levels, together with the distribution of different subsets of blood monocytes and DCs, were investigated. Results SM patients showed increased plasma levels and spontaneous production by blood monocytes of IL1β, IL6, IL8, TNFα and IL10, associated with an exhausted ability of LPS + IFNγ‐stimulated blood monocytes to produce IL1β and TGFβ. SM (particularly ISM) patients also showed decreased counts of total monocytes, at the expense of intermediate monocytes and non‐classical monocytes. Interestingly, while ISM and ASM patients had decreased numbers of plasmacytoid DC and myeloid DC (and their major subsets) in blood, an expansion of AXL+ DC was specifically encountered in BMM cases. Conclusion These results demonstrate an altered distribution of blood monocytes and DC subsets in SM associated with constitutive activation of functionally impaired blood monocytes and increased plasma levels of a wide variety of inflammatory cytokines, reflecting broad activation of the innate immune response in mastocytosis.

T‐cell immune profile in blood of systemic mastocytosis: Association with disease features

“…results confirm and extend on previous data 22 about the existence of significantly decreased counts of both TCD4 − cytotoxic and NK cells in blood of SM patients compared to agematched HD. Of note, the lower T-cytotoxic cell counts found in blood, affected all different memory and effector cell compartments (i.e., CM, TM, EE and TE cells) from BMM, ISM and ASM patients.Interestingly, such decrease in NK-and cytotoxic T-cell counts does not appear to be due to a lower BM or thymic output, because a parallel increased production and release of TCD4 − naive cells to blood associated with greater NK-cell numbers in the BM were observed.Altogether, these data suggest an increased migration of NK cells and of both memory and effector cytotoxic T cells from blood to other tissues, related to the broad innate immune cell activation previously described in SM patients 21. Likewise, detailed analysis of blood TCD4 + cells from SM patients revealed significantly decreased counts of multiple functional cell subsets, particularly of Th1 cells (and their CM, TM and TE cell compartments), in addition to Th2 EM, Th22 TE and Th1like Treg cells.…”

“…[14][15][16][17][18][19][20] Thus, recent studies from our and other groups have reported an altered distribution of monocyte and DC populations in blood of SM patients, in association with an increased spontaneous ex vivo production and secretion of inflammatory cytokines, which support a broader activation of the innate immune response in mastocytosis, responsible for the increased serum levels of proinflammatory cytokines also found in these patients. 21,22,24 In addition to these inflammatory cytokines, MC mediators such as histamine and tryptase are also elevated in SM and have been demonstrated in experimental models to alter the lymphocyte function. 19,34,35 In this regard, Kulinski et al, 22 found significantly lower frequencies and absolute counts of circulating NK cells and TCD8 + cells, with an increased TCD4 + / TCD8 + cell ratio, in a small cohort of 20 ISM patients among whom the altered TCD8 and NK-cell profiles were associated with specific clinical features such as osteoporosis and autoimmune diseases.…”

“…Thoroughly, the above findings suggest that constitutively activated MC from SM patients might exert direct effects on other innate immune cells, as well as on T‐lymphocytes. In this regard, previous studies have reported an altered innate immune response associated with increased numbers of activated, but functionally exhausted, monocytes and dendritic cells (DC) in blood of SM patients, in parallel to increased plasma levels of proinflammatory cytokines such as IL‐1β, IL‐6, IL‐8 and TNF‐α 21 . These immunological effects might also contribute to explain the abnormally decreased blood counts of both natural killer (NK) cells and TCD8 + T‐lymphocytes, 22 together with the increased number of circulating type II innate lymphoid cells (ILC2) 23 and TCD4 + cells, 24 previously reported in ISM 22–24 .…”

Performance of spectral flow cytometry and mass cytometry for the study of innate myeloid cell populations

“…This was due, at least in part to discrepancies between the two approaches for some markers (i.e., CD45 and CD163 showed lower resolution in MC, while CD192 and CD303 were associated with higher AOF with SFC). Overall, such discrepancies, particularly for those four markers, might be related to i) the use of different antibody clones in the two panels (e.g., for CD192 and CD303); ii) the impact of the spread of the signal in case of SFC (52), and iii) the relative brightness of the label selected, e.g., CD45 and CD163 were conjugated with 89Y and 141Pr in the MC panel, 36). Overall, this highlights the power of the combination of markers employed in the study even in cases where "reactive"/ aberrant phenotypes are present.…”

“…Two antibody panels specifically designed for the study of IMC populations were used to stain PBMC, based on previous reports (EuroFlow patent "Means and methods for multiparameter cytometry-based leukocyte subsetting"; PCT/NL2020/050688, priority date 5 November 2019) (27,(32)(33)(34)(35)(36). Briefly, the selection of the markers employed in both MC and SFC combinations was performed based on unbiased identification of the most optimal set of markers to identify each population, in order to provide the best population discrimination and avoid any type of redundancy (27, 37-41).…”