Munc13-4 deficiency with CD5 downregulation on activated CD8+ T cells

Abstract

Familial hemophagocytic lymphohistiocytosis (FHL) is characterized by uncontrolled activation of T cells and macrophages and hypercytokinemia. We have recently described a significant increase in a subpopulation of CD8(+) T cells with downregulation of CD5 during the acute phase of FHL type2 (FHL2; perforin deficiency), which declines after successful treatment, with a concomitant reduction in serum cytokine level. This unusual subset of CD8(+) T cells, however, has not been characterized in patients with other subtypes of FHL. Herein, we describe a patient with FHL3 (Munc13-4 deficiency) carrying compound heterozygous mutations in the UNC13D gene. He had high serum levels of pro-inflammatory cytokines and significantly increased activated CD8(+) T cells with downregulation of CD5 during the acute phase, similar to that found in FHL2. This immunophenotypic feature may serve as a useful marker of immune dysregulation in FHL3 in addition to FHL2.

Keywords: CD5; CD8+ T cells; Munc13-4; UNC13D; familial hemophagocytic lymphohistiocytosis.