Tet2 deficient conventional dendritic cells contribute to clonal hematopoiesis inflammation and alter immune response

Abstract

Abstract Clonal mutations accrue with age and 20% of the elderly have dominant clonal hematopoiesis. Mutations to demethylating enzymes (including Tet methylcytosine dioxygenase 2, TET2) are common in these patients and loss of functional TET2 in mature myeloid cells increases pro-inflammatory cytokine secretion (such as interleukin 6, IL-6) leading to immune cell dysfunction. Our group investigated the impact of TET2 mutations in immune cells and effects of altered hematopoiesis on non-mutated cells in chimeric mouse models. We utilized an MxCre x Tet2fl/fl mouse model on a CD45.1 background. After polyinosinic:polycytidylic acid excision, bone marrow was collected and transplanted retro-orbitally into CD45.1/CD45.2 hosts. Peripheral blood was analyzed at 8-, 14-, 18-, and 24-weeks using flow cytometry to test for engraftment of Tet2−/− cells. Mice were taken down and marrow, spleen, and mediastinal lymph nodes (medLN) were analyzed at 18- and 24-weeks of age. We saw increases by frequency and counts of TET2−/− cDCs in the spleen and medLNs along with reduced production of host cDCs. Specifically, there was a slight increase in TET2−/− cDC1s and frequency of mutant cDC2s was three times greater than host, indicating host cDCs are being outcompeted. Loss of Hdac2 acylation in TET2−/− cDCs causes sustained production of IL-6, influencing Th17 and Tfh cell production and inflammatory cytokine secretion. This suggests cDCs play a role in disease progression and altering immune response. Mutant and disease-exposed cDCs are being explored using scRNAseq and ATACseq in combination with functional assays to determine gene regulatory networks governing mutant pro-inflammatory mechanisms and consequences in the education of adaptive immunity.