Physiology, Immune Response

The immune response is the body's ability to stay safe by protecting against harmful agents. The response involves lines of defense against most microbes and specialized and highly specific responses to particular offenders. This immune response is either innate, nonspecific, adaptive acquired, or highly specific. The innate response, often our first defense against anything foreign, defends the body against a pathogen. These natural mechanisms include the skin barrier, saliva, tears, cytokines, complement proteins, lysozyme, bacterial flora, and numerous cells, including neutrophils, basophils, eosinophils, monocytes, macrophages, reticuloendothelial system, natural killer cells, epithelial cells, endothelial cells, red blood cells, and platelets.

The adaptive acquired immune response uses the ability of specific lymphocytes and their products, such as immunoglobulins and cytokines, to generate a response against the invading microbes. The typical features include:

1. Specificity: The triggering mechanism is a particular pathogen, immunogen, or antigen.

1. Heterogeneity: Signifies the production of millions of different effectors of the immune response (antibodies) against millions of intruders.

1. Memory: The immune system has the ability not only to recognize the pathogen on its second contact but also to generate a faster and stronger response.

The inflammatory immune response is innate immunity that blocks the entry of invading pathogens through the skin, respiratory, or gastrointestinal tract. If pathogens can breach the epithelial surfaces, they encounter macrophages in the subepithelial tissues that attempt to engulf them and produce cytokines to amplify the inflammatory response. Active immunity results from the immune system's response to an antigen and, therefore, is acquired. Immunity resulting from the transfer of immune cells or antibodies from an immunized individual is passive immunity. The immune system has evolved to maintain homeostasis to discriminate between foreign antigens and self; however, an autoimmune reaction or disease develops when this specificity is affected.