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Immunity is required for us to protect ourselves from infectious diseases. They are two different types of immunity that occur in our bodies, innate immunity and adaptive immunity.
Innate immunity provides the very first defense against the infectious disease . An immediate maximal response takes place in innate immunity and responds to all antigens in turn to protect us from the infection. Innate immunity or the nonspecific immune system consists of anatomical barriers such as the skin where the epithelial surface forms an impermeable barrier to most infections or mucosal membranes that are covered in epithelium also are successful barriers towards the pathogens. Epithelia has its very own defense mechanism such as stopping the pathogen from adhering on to the epithelium and it also secretes antimicrobial enzymes. The acidity in our stomachs are a chemical barrier to organisms by not allowing them to grow in those conditions. We also contain an enzyme called lysozyme which is usually found in our tears that breaks down the cells wall of certain bacteria. These barriers are very important as a loss of these barriers in an individual can cause serious harm and will need to be treated with drugs to prevent infections .
Apart from physical barriers there is also another important defense mechanism of the innate system. Inflammation occurs to protect the body when the bodies' tissue is injured. The main aim is to get rid of all the pathogens and damaged cells and start a recovery process. It's not antigen specific and hence it is a part of the innate immune system. It is a very important process as without inflammation healing would not occur . Also an inflammatory response concentrates components of innate immunity at the site of inflammation. Hence this causes a specific immune response to the invader. This immune response is known as the adaptive immune response.
Consequently, Phagocytosis occurs during innate immunity in which extracellular material is ingested. Due to inflammation the phagocytes can enter and reach the target site. Phagocytes are a type of cells that can engulf and destroy the microorganism. The main steps of phagocytosis include engulfment by endocytosis, bacterium being ingested by a phagosome, an enzyme called lysozyme combining with the phagosome which allows them to release their contents to form a phagolysosome. This is the place where the intracellular killing and intracellular digestion of the bacteria occurs . Phagocytosis involves a series of special cells such as monocytes, macrophages and neutrophils. In addition to that dendritic cells and macrophages make the initial interaction with the pathogen. In lymph nodes and spleen dendritic cells play a role as antigen presenting cells where the antigens get presented to the helper T cells in the lymphocytes. This is very important to start an adaptive immune response .
The innate immune system contains several different receptors which are known as PRRs (pattern recognition receptors). Toll like receptor is one of the five PRRs that recognizes microbial elements and initiates signal transduction pathways . These receptors can then bind to the PAMPs (pathogen associated molecular patterns). Once the PRRs have bound to the PAMPs, the receptor sends a signal to the other molecules via a cascading response. This results in an activation of the immune cell. This will cause the cell to up regulate its expression of stimulatory molecules and will also release molecules involved with signaling such as cytokines and chemokine's. This allows information about the infection to be passed on to other immune cells which effects the developing adaptive response. If we look at dendritic cells they digest the microbe and then present them on themselves as antigens. They then receive signals from chemokines and cytokines that were initially released by other innate immune cells. This makes them move from the site of infection to secondary lymphatic tissues. The dendritic cells then display the antigen which contains the pathogen to the B cells and T cells in the adaptive system. If these cells manage to recognize the antigen on the dendritic cell then an adaptive immune response occurs hence dendritic cells are a very important component of our immunity as it links the innate immune response to the adaptive immune response by delivering the ingested pathogen in form of antigen to the secondary lymphoid organs .
The adaptive immune response is a longer lasting response than the innate immune system. It consists of antibody responses (humoral immunity) and cell mediated responses. These are carried out by two different types of cells known as B lymphocytes (B cells) and T lymphocytes (T cells).In antibody responses, B cells produce antibodies which circulate in the blood plasma. They then bind to the foreign antigen which results in deactivation of toxins as they cannot bind to the receptors on host cells anymore .
However, cell mediated immunity doesn't involve antibodies. Cell mediated immunity can only be transferred by T cells from an individual who is immune. In this type of immunity various different types of T cells recognize antigen present on self-cells. T helper cells will interact with an antigen on production of cytokines. Whereas cytotoxic T cells will interact to antigen by developing into cytotoxic T lymphocytes. This will cause killing of altered self cells.
Finally, we can say that innate immunity is required for an adaptive immune response. They aren't independent to each other. They manage to produce a very effective immune response when working together. To produce an effective immune response we need the macrophages of the innate system to interact with the microbial components in order to produce cytokines that will then in turn generate a direct adaptive immune response. However the adaptive immune system also helps by producing signals which makes the innate response even more effective. For example when some T cells encounter the correct antigen, they then produce and secrete cytokines. This helps the macrophage to destroy the microbe they have digested. Even though the innate system is more rapid and the adaptive system is more specific, we still need both to produce an effective immune response.
Summary of how the innate system affects the adaptive response
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