Increased Frequency of CD4+ Follicular Helper T and CD8+ Follicular T Cells in Human Lymph Node Biopsies during the Earliest Stages of Rheumatoid Arthritis.

Follicular T helper cells (Tfh cells) provide key B-cell help and are essential in germinal center formation and (auto) antibody generation. To gain more insight into their role during the earliest phase of rheumatoid arthritis (RA), we analyzed their frequencies, phenotypes, and cytokine profiles in peripheral blood and lymph node biopsies of healthy controls (HCs), autoantibody-positive individuals at risk for developing RA (RA-risk individuals), and early RA patients. Subsequently, we confirmed their presence in lymph nodes and synovial tissue of RA patients using immunofluorescence microscopy. In the blood, the frequency of Tfh cells did not differ between study groups. In lymphoid and synovial tissues, Tfh cells were localized in B-cell areas, and their frequency correlated with the frequency of CD19+ B cells. Compared to lymphoid tissues of healthy controls, those of RA patients and RA-risk individuals showed more CD19+ B cells, CD4+CXCR5+ follicular helper T cells, and CD8+CXCR5+ follicular T cells. These Tfh cells produced less IL-21 upon ex vivo stimulation. These findings suggest that Tfh cells may present a novel rationale for therapeutic targeting during the preclinical stage of RA to prevent further disease progression.

Bimodal expression of potential drug target CLL-1 (CLEC12A) on CD34+ blasts of AML patients.

OBJECTIVES: This study aims to retrospectively assess C-lectin-like molecule 1 (CLL-1) bimodal expression on CD34+ blasts in acute myeloid leukemia (AML) patients (total N = 306) and explore potential CLL-1 bimodal associations with leukemia and patient-specific characteristics. METHODS: Flow cytometry assays were performed to assess the deeper immunophenotyping of CLL-1 bimodality. Cytogenetic analysis was performed to characterize the gene mutation on CLL-1-negative subpopulation of CLL-1 bimodal AML samples. RESULTS: The frequency of a bimodal pattern of CLL-1 expression of CD34+ blasts ranged from 8% to 65% in the different cohorts. Bimodal CLL-1 expression was most prevalent in patients with MDS-related AML (P = .011), ELN adverse risk (P = .002), NPM1 wild type (WT, P = .049), FLT3 WT (P = .035), and relatively low percentages of leukemia-associated immunophenotypes (P = .006). Additional immunophenotyping analysis revealed the CLL-1- subpopulation may consist of pre-B cells, immature myeloblasts, and hematopoietic stem cells. Furthermore, (pre)-leukemic mutations were detected in both CLL-1+ and CLL-1- subfractions of bimodal samples (N = 3). CONCLUSIONS: C-lectin-like molecule 1 bimodality occurs in about 25% of AML patients and the CLL-1- cell population still contains malignant cells, hence it may potentially limit the effectiveness of CLL-1-targeted therapies and warrant further investigation.

Human lymph-node CD8(+) T cells display an altered phenotype during systemic autoimmunity.

Although many studies are focused on auto-reactive CD4(+) T cells, the precise role of CD8(+) T cells in autoimmunity is poorly understood. The objective of this study is to provide more insight into the phenotype and function CD8(+) T cells during the development of autoimmune disease by studying CD8(+) T cells in human lymph-node biopsies and peripheral blood obtained during the earliest phases of rheumatoid arthritis (RA). Here, we show that lymphoid pro-inflammatory CD8(+) T cells exhibit a less-responsive phenotype already during the earliest phases of autoimmunity compared with healthy individuals. We found an increase in CD8(+) memory T cells in lymphoid tissue during the earliest phases of autoimmunity, even before clinical onset of RA, accompanied by an increased frequency of non-circulating or recently activated (CD69(+)) CD8(+) T cells in lymphoid tissue and peripheral blood. Importantly, lymphoid pro-inflammatory CD8(+)IL-17A(+) T cells displayed a decreased capacity of cytokine production, which was related to disease activity in early RA patients. In addition, a decreased frequency of regulatory CD8(+)IL-10(+) T cells in peripheral blood was also related to disease activity in early RA patients. Our results suggest that different CD8(+) T-cell subsets are affected already during the earliest phases of systemic autoimmunity.