The Role of Collectins and Galectins in Lung Innate Immune Defense

Abstract

Different families of endogenous lectins use complementary defense strategies against pathogens. They may recognize non-self glycans typically found on pathogens and/or host glycans. The collectin and galectin families are prominent examples of these two lectin categories. Collectins are C-type lectins that contain a carbohydrate recognition domain and a collagen-like domain. Members of this group include surfactant protein A (SP-A) and D (SP-D), secreted by the alveolar epithelium to the alveolar fluid. Lung collectins bind to several microorganisms, which results in pathogen aggregation and/or killing, and enhances phagocytosis of pathogens by alveolar macrophages. Moreover, SP-A and SP-D influence macrophage responses, contributing to resolution of inflammation, and SP-A is essential for tissue-repair functions of macrophages. Galectins also function by interacting directly with pathogens or by modulating the immune system in response to the infection. Direct binding may result in enhanced or impaired infection of target cells, or can have microbicidal effects. Immunomodulatory effects of galectins include recruitment of immune cells to the site of infection, promotion of neutrophil function, and stimulation of the bactericidal activity of infected macrophages. Moreover, intracellular galectins can serve as danger receptors, promoting autophagy of the invading pathogen. This review will focus on the role of collectins and galectins in pathogen clearance and immune response activation in infectious diseases of the respiratory system.

Analysis of the SARS-CoV-2 spike protein glycan shield reveals implications for immune recognition

“…Fortunately, the innate immune system has evolved a range of strategies for responding to glycosylated pathogens 10 , but antigen glycosylation nevertheless complicates the development of vaccines 11 . Over time, the protein sequences in viral antigens undergo mutations (antigenic drift), which can alter the species specificity of the virus 12 , modulate its infectivity 13 , and alter the antigenicity of the surface proteins 14 .…”

Analysis of the SARS-CoV-2 spike protein glycan shield: implications for immune recognition

“…The glycosylation of these surface antigens helps the pathogen evade recognition by the host immune system by cloaking the protein surface from detection by antibodies, and can influence the ability of the host to raise an effective adaptive immune response 3,4 or even be exploited by the virus to enhance infectivity 5 . Fortunately, the innate immune system has evolved a range of strategies for responding to glycosylated pathogens 6 , but antigen glycosylation nevertheless complicates the development of vaccines 7 . Over time, the protein sequences in viral antigens undergo mutations, which can alter the species specificity of the virus 8 , modulate its infectivity 9 , and alter the antigenicity of the surface proteins 10 .…”

Galectin-3 inhibits Paracoccidioides brasiliensis growth and impacts paracoccidioidomycosis through multiple mechanisms

“…Herein we describe a role for Gal-3 in P. brasiliensis infection that parallels recent observations with C. neoformans (13). Galectins are able to regulate positively or negatively host-microbial interactions in respiratory infections according to galectin type, pathogen and host context (28, 29). Gal-3, member of the galectin family of β-galactosides-binding proteins, is widely expressed in different cells, and plays important roles in biological phenomena, such as inflammation and immunity (28, 30).…”