Host Immune Responses Against Type A Influenza Viruses

ABSTRACT

The influenza viruses are divided into 3 different types, A, B and C, all of them are known as human pathogens. However, only type A influenza viruses cause both epidemic and pandemic influenza. Typically, influenza virus infects a respiratory tract, targets a lung and causes an acute infectious disease. Influenza infection can be identified by a high fever, headache, body ache and extreme fatigue. Host immune system against Influenza infection consists of innate immune response and adaptive immune response. Innate immune responses include recognition of influenza viruses by alveolar macrophages and natural killer cells. Adaptive immune responses contain influenza virus specific antibody production by B cells and killing infected cells by cytotoxic T cells. Initially, influenza viruses are recognized by pattern recognition receptors (PRRs) on respiratory epithelial cells and alveolar macrophages, which can induce efficient anti-viral immune responses. Host immune responses play crucial roles in defense against influenza virus infection but sometimes these may contribute to immuno-pathology, which results in serious tissue damage. In this review, we went over the understanding of current literature on subtypes of influenza A viruses, important viral antigens and anti-viral immune mechanisms.