Background Vδ1+ T cells, a subset of γδ T cells, are responsible for innate‐like immune responses. Recently, an anti‐tumor function mediated by MHC‐unrestricted recognition of lipid and stress molecules, has also been described in these cells. This study aimed to quantify and phenotypically characterize circulating Vδ1+ T cells in B cell Chronic Lymphocytic Leukemia (CLL) and Monoclonal B cell lymphocytosis (MBL). Methods This study enrolled 58 individuals distributed in five groups: Binet B and C CLL (n = 9), Binet A CLL (n = 26), High count‐MBL (n = 10), Low count‐MBL (n = 5), and a control group (n = 8). The phenotypic characterization of Vδ1+ T cells, as well as the other T cell subpopulations (CD4+, CD8+, CD4+/CD8+, and Vδ1− γδT cells), were assessed by flow cytometry, evaluating the frequency of each subset expressing CD27, CD69, and cytoplasmic granzyme B. Results We observed an increasing percentage of Vδ1+ T cells belonging to CD27− compartment from controls to advanced stages of the disease, which was accompanied by an increasing percentage of these cells expressing granzyme B, a phenotypic pattern that was also observed in the other T cell subpopulations under study since earlier stages of the disease. Moreover, a striking expansion of Vδ1+ T cells in Binet B and C CLL was observed. Conclusions These experiment findings point to an expansion of CD27‐Vδ1+ T cells with a cytotoxic profile, from controls to advanced stages of the disease, which points to a role of Vδ1+ T cells in the host's anti‐tumor responses against clonal B‐cells in MBL and CLL. © 2018 Clinical Cytometry Society

A broad understanding on how SARS-CoV-2 infection and vaccination mobilize the immune system is necessary to find the best predictors of long-term protection and identify individuals that would benefit from additional vaccine doses. This study aims to understand the effect of a single dose of Pfizer-BioNTech BNT162b2 COVID-19 vaccine, in individuals recovered from SARS-CoV-2 infection, on circulating CD4 + T follicular helper (Tfh)-cells, Spike-specific T-cells and IgG/IgA antibodies. For that, peripheral blood samples from 50 healthcare professionals, recovered from SARS-CoV-2 infection, collected immediately before (T1) and 15 days after (T2) vaccine administration, were used to analyze the frequency and numbers of Tfh-cells and their subsets, serum titers of SARS-CoV-2-specific antibodies, and SARS-CoV-2-specific T-cells. Six months after infection (T1), 96% of recovered participants presented either IgG or T-cells specific for Spike, however, Spike-specific T-cells were missing in 16% of them. These individuals presented lower levels of Spike-specific IgG (T1 and T2), IgA (T1), and Spike-specific T-cells (T2). Vaccination increased the percentage of participants reactive for Spike-specific T-cells (from 64 to 98%), IgG (from 90 to 100%) and IgA (from 48 to 98%). It also mobilized circulating Tfh-cells, increasing their frequency and activation, and promoting Tfh17 polarization, restoring the decreased numbers of Tfh-cells (especially Tfh17) observed in recovered participants. Interestingly, Tfh percentage correlated with Spike-specific IgG levels. Our data showed that a single dose of vaccine efficiently restored Spike-specific T-cells, and IgG and IgA antibodies. Mobilization of Tfh-cells, and their correlation with IgG levels, suggest that vaccination induced a functional Tfh cell response. Supplementary Information The online version contains supplementary material available at 10.1007/s10238-022-00801-8.