Unexpected expression of peptidoglycan recognition protein 2 in lymphocytes and bone marrow hematopoietic stem cells (87.8)

Abstract

Abstract Peptidoglycan recognition factors are highly conserved molecules involved in recognition of fragments of bacterial peptidoglycans in innate immune responses. Peptidoglycan recognition protein 2 (PGLYRP2) is a serum N-acetylmuramoyl-alanine amidase secreted by the liver. We used a green fluorescent reporter allele engineered into the gene to label cells in the mouse that endogenously express PGLYRP2. Unexpectedly, PGLYRP2 was expressed constitutively in resting CD4 and CD8 lymphocytes and in NK cells. Reconstitution of PGLYRP2-deficient mice with PGRLYRP2-sufficient T cells led to the accumulation of PGLYRP2 in serum. In assessing bone marrow populations in these mice, we identified constitutive PGLYRP2 expression in a subset of lineage-negative, c-kit+Sca1+ cells that had the properties of hemopoietic stem cells, including the capacity to establish hematopoietic lineages and for self renewal when transferred into irradiate recipient mice. Expression of PGLYRP2 was also confirmed within the conventionally identified hematopoietic stem cell compartment in wildtype mice, confirming the unexpected expression of this enzyme in bone marrow stem cells.