Novel leukolectin proteins (LLs) are present in multiple lower vertebrates. Secreted LL-proteins (~236 AAs) possess five TECPR-domains spanning most of the conserved primary sequences. LL-proteins are detected in dermal lectocytes, (primitive and tissue resident) macrophages and some leukocytes. Hatched fish embryos use secreted LLs for innate immunity defense. LL genes have 4 introns, 5 exons, and multiple 5' upstream binding sites for hematopoietic transcription factors. The aim of this study was to identify potential LLs in human leukocytes. Western blots of protein extracts (resolved by 2D polyacrylamide gel electrophoresis) exclusively revealed LLs (molecular weight ∼30 kDa; isoelectric point ∼6.0), but only in PolymorphPrep-enriched leukocytes, not in Lymphoprep-enriched leukocytes. Single-label immuno-fluorescence demonstrated LLs in some polymorphonuclear (PMN) leukocytes. Dual-label immunofluorescence corroborated LL coexpression in some myeloperoxidase-positive neutrophils (which we denote lectophils). Intervillous spaces in placentas collected from cesarean delivery births had both lectophils and large lectophils without well-defined PMN nuclei. Some moderately LL-positive placental endothelium appeared to cytodifferentiate with intensified LL expression to large, non-PMN lectophils for circulation. Functional distinctions between nonlectophilic neutrophils and lectophilic neutrophils await experimental delineation.
Keywords: lectophils; leukolectins; neutrophils; placental lectophils.
© The Author(s) 2026. Published by Oxford University Press on behalf of Society for Leukocyte Biology.