Innate immunity in vertebrates: an overview

Abstract

SummaryInnate immunity is a semi-specific and widely distributed form of immunity, which represents the first line of defence against pathogens. This type of immunity is critical to maintain homeostasis and prevent microbe invasion, eliminating a great variety of pathogens and contributing with the activation of the adaptive immune response. The components of innate immunity include physical and chemical barriers, humoral and cell-mediated components, which are present in all jawed vertebrates. The understanding of innate defence mechanisms in non-mammalian vertebrates is the key to comprehend the general picture of vertebrate innate immunity and its evolutionary history. This is also essential for the identification of new molecules with applications in immunopharmacology and immunotherapy. In this review, we describe and discuss the main elements of vertebrate innate immunity, presenting core findings in this field and identifying areas that need further investigation.

Innate-like B cell subsets during immune responses: Beyond antibody production

“…Anatomical and physiological barriers that include the skin and mucosal surfaces, mucociliary clearance function, low stomach pH and lysozyme activity in tears, saliva, and other secretions together provide the very first line of defense against pathogens …”

“…Innate immunity mechanisms represent the second line of defense and depend on both cells and molecules recognizing conserved patterns of pathogens that are not present in the host. The components of the innate immune system are rapidly activated upon encountering any danger signal to maintain a healthy microenvironment . The innate immune cells and molecules typically include phagocytic cells such as polymorphonuclear leukocytes, monocytes and Mϕs, APCs, NK cells, natural Abs, complement system components, and germline‐encoded pattern recognition receptors .…”

“…The components of the innate immune system are rapidly activated upon encountering any danger signal to maintain a healthy microenvironment . The innate immune cells and molecules typically include phagocytic cells such as polymorphonuclear leukocytes, monocytes and Mϕs, APCs, NK cells, natural Abs, complement system components, and germline‐encoded pattern recognition receptors . These fundamental elements of the innate immune system can also secrete soluble mediators such as cytokines and chemokines to improve their ability to recognize and deal with diverse danger signals …”

Expression profiles of two thaumatin‐like protein (TmTLP) genes in responses to various micro‐organisms fromTenebrio molitor

“…Humoral immune responses mainly depend on antimicrobial peptides (AMPs) secreted from various immune cells such as the fat body, hemocytes, gut epithelial cells and Malpighian tubules through either the Toll and/or the immune deficiency (IMD) signaling cascade (Imler ; Riera Romo et al . ). As a result of humoral immune responses, the fruit fly ( Diptera ) secretes various types of AMPs, such as drosomycin (Landon et al .…”

SNP‐based susceptibility–resistance association and mRNA expression regulation analyses of tlr7 to grass carp Ctenopharyngodon idella reovirus

“…The immune system is responsible for clearing invading pathogens that can establish themselves to cause disease. Innate immune system, as the first line of defence against diverse repertoire of invading microorganisms, discriminates between self and non‐self and plays a central role in triggering and optimizing the adaptive immune response (Zhang & Gui, ; Noreen & Arshad, ; Riera Romo et al, ). The recognition of pathogen‐associated molecular patterns (PAMP) is a pivotal step for host innate immunity.…”