Non-eosinophilic leukolectin-proteins occur in cytoplasmic granules in some human leukocytes.

Novel leukolectin-proteins (LL-proteins) are present in multiple lower vertebrates. LL-proteins (∼255 AAs) possess five TECPR-domains spanning 4/5 of conserved AA-sequences, and are detected in dermal lectocytes, (primitive and tissue resident) macrophages and some leukocytes. Hatched fish embryos employ secreted LL-proteins for innate immunity-defense. LL-genes display 4 introns, 5 exons and multiple 5'-upstream binding-sites for hematopoietic transcription-factors. This study aims to identify potential LL-proteins in human leukocytes. Western-blots of protein-extracts (resolved by 2D-PAGE) exclusively revealed LL-proteins (MW ̴̴30 kD; pI ̴6.0), but only in PolymorphprepTM-enriched leukocytes, and not in LymphoprepTM-enriched leukocytes. Single-label immuno-fluorescence demonstrated LL-proteins in some PMN-leukocytes. Dual-label immuno-fluorescence corroborated LL-coexpression in some myeloperoxidase-positive neutrophils (denoted lectophils). Intervillous spaces in Caesarean placentas displayed 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 non-lectophilic neutrophils and lectophilic neutrophils await experimental delineation.