[5][7] Håkan Steiner and coworkers, using a differential display screen, identified and cloned Peptidoglycan Recognition Protein (PGRP) in a moth (Trichoplusia ni) and based on this sequence discovered and cloned mouse and human PGRP orthologs.

[7] Human PGRP was a founding member of a family of four PGRP genes found in humans that were named PGRP-S, PGRP-L, PGRP-Iα, and PGRP-Iβ (for short, long, and intermediate size transcripts, by analogy to insect PGRPs).

PGLYRP1 is highly constitutively expressed in the bone marrow[5][9][11] and in the tertiary granules of polymorphonuclear leukocytes (neutrophils and eosinophils),[11][12][13][14][15][16] and to a lesser extent in activated macrophages[15][16] and fetal liver.

[9] PGLYRP1 is also expressed in lactating mammary gland,[17] and to a much lower level in corneal epithelium in the eye,[18] in the inflamed skin,[19][20] spleen,[5] thymus,[5] and in epithelial cells in the respiratory[15][16] and intestinal tracts.

[9][10] Human PGLYRP1 has a 25 Å-long peptidoglycan-binding cleft whose walls are formed by two α-helices and the floor by a β-sheet.

[30][32] The structure of the disulfide-linked dimer is unknown, as the crystal structure of only monomeric human PGLYRP1 was solved, because the crystallized protein lacked the 8 N-terminal amino acids, including Cys8,[10] which is likely involved in the formation of the disulfide-linked dimer.

PGLYRP1 binds peptidoglycan, a polymer of β(1-4)-linked N-acetylglucosamine (GlcNAc) and N-acetylmuramic acid (MurNAc) cross-linked by short peptides, the main component of bacterial cell wall.

[39] Human PGLYRP1 is directly bactericidal for both Gram-positive (Bacillus subtilis, Bacillus licheniformis, Lactobacillus acidophilus, Staphylococcus aureus, Streptococcus pyogenes) and Gram-negative (Escherichia coli, Proteus vulgaris, Salmonella enterica, Shigella sonnei, Pseudomonas aeruginosa) bacteria,[12][14][32][34][40] and a spirochete Borrelia burgdorferi.

[37] PGLYRP1 limits intracellular survival of Listeria monocytogenes in macrophages[41] and is also active against Chlamydia trachomatis.

[40] In both Gram-positive and Gram-negative bacteria PGLYRP1 stays bound to the cell envelope and does not enter the cytoplasm.

[40] The mechanism of killing by PGLYRP1 is based on induction of lethal envelope stress and production of reactive oxygen species in bacteria and the subsequent shutdown of transcription and translation.

[21][45][46] Mouse PGLYRP1 plays a role in maintaining anti- and pro-inflammatory homeostasis in the intestine, skin, lungs, joints, lymphoid organs, eyes, and brain.

[15] The pro-inflammatory effect of PGLYRP1 on asthma depends on the PGLYRP1-regulated intestinal microbiome, because this increased resistance to experimentally induced allergic asthma could be transferred to wild type germ-free mice by microbiome transplant from PGLYRP1-deficient mice.

[37] PGLYRP1 fused to the Fc region of mouse IgG2a increases survival and ameliorates lung injury and inflammation in a mouse model of E. coli-induced acute respiratory distress syndrome, without affecting bacterial clearance.

[48] This PGLYRP1-Fc construct suppresses macrophage activation through the Fc gamma receptor (FcγR)-dependent mechanism, thus reducing inflammatory damage to the lungs.

[53] PGLYRP1-Hsp70 complexes bind to the TNFR1 (tumor necrosis factor receptor-1, which is a death receptor) and induce a cytotoxic effect via apoptosis and necroptosis.

[56] They also decrease inflammatory responses in a mouse model of acute lung injury[56] and in the complete Freund's adjuvant-induced arthritis in mice.

[88] Umbilical cord blood serum concentration of PGLYRP1 is inversely associated with pediatric asthma and pulmonary function in adolescence.