author(s)
Anushri Tiwari, Madhu Swamy and Prateek Mishra

abstract
The immunosuppressive diseases in today’s era has led to heavy burden of economic losses on the poultry farmers as these diseases lead to wiping out of the entire flocks at a stroke due to poor growth rate and heavy mortality. Avian immune response cannot be appreciated without knowing its basic structure. Thus, understanding of the immune system and the deleterious effects caused bacterial, viral, parasitic and neoplastic diseases on the immune system becomes necessary. Most infectious organisms stimulate immune responses within every compartment of the immune system. Resistance to infectious agents may depend upon innate mechanisms or acquired immune responses. Inflammation, phagocytosis, cell-mediated immunity and antibodies are components of a complex reaction which result either in resistance or in susceptibility. The innate and adaptive immune responses are owned by both mammals and avian and the avian adaptive immune response involving both cell-mediated and humoral immune responses, promoting immunological memory and helps fight against the pathogens.