Structure-function and application of plant lectins in disease biology and immunity

Abstract

Lectins are proteins with a high degree of stereospecificity to recognize various sugar structures and form reversible linkages upon interaction with glyco-conjugate complexes. These are abundantly found in plants, animals and many other species and are known to agglutinate various blood groups of erythrocytes. Further, due to the unique carbohydrate recognition property, lectins have been extensively used in many biological functions that make use of protein-carbohydrate recognition like detection, isolation and characterization of glycoconjugates, histochemistry of cells and tissues, tumor cell recognition and many more. In this review, we have summarized the immunomodulatory effects of plant lectins and their effects against diseases, including antimicrobial action. We found that many plant lectins mediate its microbicidal activity by triggering host immune responses that result in the release of several cytokines followed by activation of effector mechanism. Moreover, certain lectins also enhance the phagocytic activity of macrophages during microbial infections. Lectins along with heat killed microbes can act as vaccine to provide long term protection from deadly microbes. Hence, lectin based therapy can be used as a better substitute to fight microbial diseases efficiently in future.

Keywords: Antimicrobial action; Immune responses; Lectins; Microbes.

Fig. 1

Classification of plant lectins.

Fig. 2

Ribbon drawing of different lectins based on structural classifications. Crystal structures of amaranthin lectin (A, first member of the amaranthin family, PDB code 1JLX), WGA (B, first isolate of chitin binding lectin family, PDB code 1WGC), pumpkin lectin (C, member of cucurbitaceae phloem lectin family, PDB code 1MIT), jacalin lectin (D, members of jacalin related lectins family, PDB code 1JAC), SBL (E, member of legume lectin family, PDB code 1SBF), Galanthus nivalis agglutinin (GNA) (F, member of mannose binding lectin family, PDB code 1JPC) and ricin (G, member of Type-2 ribose inactivating lectin family, PDB code 2AAI).

Fig. 3

Generalized and advanced applications of plant lectins.