Innate vs Adaptive Immunity
The major function of the immune system is to defend the host against pathogens and toxins, a task which is essential to any organism. Rather than forming into organs, the cells of the immune system are composed primarily of individual cells, and they spread throughout the body. However, these cells of the immune system work in a cooperative manner, to complete their task for our body. The unique characteristic feature of the immune system is that it can recognize its own molecules from foreign molecules. Generally an immune response involves a number of key stages; namely, pathogen recognition, activation and initiation, regulation, and the generation of immunological memory. Vertebrate immune system can be dived into two basic branches; innate and adaptive immunity. Although those immunities have different roles, they generally act together in fighting an infection.
The innate immune system is also known as the nonspecific immune system, which provides the first line of immunological defense against infection. The molecules and the receptors of the immune system provide a broad range of protection, so that it is also referred to as ‘natural immunity’. It generates a diverse set of molecules that can recognize virtually any invading pathogen. Basically, the first response is slow and highly specific to invading pathogens. However, the response to a second attack is more rapid, and it is the basis for vaccines.
The innate system is mainly composed of eosinophils, monocytes, macrophages, natural killer cells, tor-like receptors (TLRs), and a series of soluble mediators such as complement system.
The adaptive or specific immune system mainly attacks the specific invaders. It consists of highly specialized cells called thymus-derived T lymphocyte cells and bone marrow-derived B lymphocyte cells. These cells are capable of recognizing different foreign antigens in a very precise way and have the capacity to generate immunological memory, so that it allows recognizing the pathogens which have encountered before.
The adaptive immunity can be divided into two types; humoral immunity and cellular immunity. Humoral immunity is mediated by antibody molecules secreted by B lymphocyte that can neutralize the pathogens outside the cells, and cellular immunity is mediated by T lymphocyte, which can eliminate infected cells and provide help to other immune responses.
What is the difference between Innate Immunity and Adaptive Immunity?
• The innate immune system is composed of physical and chemical barriers, phagocytic leukocytes, dendritic cells, natural killer cells, and plasma proteins whereas the adaptive immune system is composed of B cells and T cells.
• The response of the innate system is rapid while that of the adaptive immunity is slow (Over 1-2 weeks).
• The innate system has limited and lower potency. In contrast, the adaptive system has high potency.
• The innate system recognizes a broad range of pathogens, but it cannot make fine distinctions. In contrast, the adaptive system recognizes highly specific antigens.
• The innate system cannot react with equal potency upon repeated exposure to the same pathogen while the adaptive system can remember the specific pathogens which have encountered before.
• The innate immune system is evolutionary, older and is found in both vertebrates and invertebrates, but the adaptive immunity system has been developed recently and is found only in the vertebrates.