CARBOHYDRATE-BINDING PROTEINS (PLANT HUMAN LECTINS AND AUTOANTIBODIESFROM HUMAN SERUM) AS MEDIATORS OF RELEASE OF LYSOZYME, ELASTASE, AND MYELOPEROXIDASE FROM HUMAN NEUTROPHILS

Analysis of cell surface glycosylation not only provides information a bout cell properties such as their state of differentiation or histoge netic lineage. The carbohydrate chains also provide potentially functi onal binding sites to endogenous carbohydrate-binding proteins. This i nteraction can elicit consequent signalling processes. Because of the importance of neutrophils in the host defence system, we monitored the effect of the binding of such sugar receptors to their cell surface o n the release of the enzymatic activities of lysozyme, elastase, and m yeloperoxidase. Besides the mannose-binding lectin concanavalin A and the immunomodulatory alpha/beta-galactoside-binding lectin from Viscum album L., three preparations of human sugar receptors - beta-galactos ide-binding lectin (M(r) 14 kDa) and two affinity-purified polyclonal IgG fractions from serum with the capacity to recognize alpha- or beta -galactosides, respectively - were used. Two animal lectins from chick en liver and intestine that bind beta-galactosides, as well as the lec tin-like human serum amyloid P component, were included in order to as sess the importance of slight differences in ligand recognition. Cytoc halasin B-enhanced enzyme release was invariably seen with the two pla nt lectins and the chicken liver beta-galactoside-binding lectin, but the related intestinal lectin did not increase enzyme release. The mam malian homologue of these avian lectins triggered lysozyme secretion, and the lactoside-binding IgG fraction enhanced the amount of extracel lular elastase activity slightly but significantly. Thus, the actual l ectin, not the nominal specificity of sugar receptors, is crucial for elucidation of responses. Due to the highly stimulatory activity of th e two plant lectins, neutrophils from patients with non-cancerous dise ases and from patients with lung cancer were monitored for the extent of lectin-mediated enzyme release. Only the concanavalin A-mediated re activity of the neutrophils was associated with the type of disease.