Immunocalins: a lipocalin subfamily that modulates immune and inflammatoryresponses

A subset of the lipocalins, notably alpha (1)-acid glycoprotein, alpha (1)- microglobulin, and glycodelin, exert significant immunomodulatory effects i n vitro. Interestingly, all three are encoded from the q32-34 region of hum an chromosome 9, together with at least four other lipocalins (neutrophil g elatinase-associated lipocalin, complement factor gamma -subunit, tear prea lbumin, and prostaglandin D synthase) that also may have anti-inflammatory and/or antimicrobial activity. This review addresses important features of this genetically linked subfamily of lipocalins (involvement with the acute phase response, immunomodulatory and anti-inflammatory properties, the tis sue localization, complex formation with other proteins and receptors, etc. ). It is likely that these proteins have evolved to be an integrated part, of the body's defense system as part of the extended cytokine network. Its members exert a regulatory, dampening influence on the inflammatory cascade , thereby protecting against tissue damage from excessive inflammation. Tha t most major mammalian allergens are lipocalins may reflect this connection of lipocalins with the immune system. We propose that this immunologically active lipocalin subset be named the 'immunocalins', signifying not only t he structural homology and close genetic linkage of its members, but also t heir protective involvement with immunological and inflammatory processes. As immune mediators, immunocalins appear to use at least three interactive sites: the lipocalin 'pocket', binding sites for other plasma proteins, and binding sites for cell surface receptors. (C) 2000 Elsevier Science B.V. A ll rights reserved.