The Innate vs. Adaptive Immune Response
The first line of defense against non-self pathogens is the innate, or non-specific, immune response. The innate immune response consists of physical, chemical and cellular defenses against pathogens. The main purpose of the innate immune response is to immediately prevent the spread and movement of foreign pathogens throughout the body.
The second line of defense against non-self pathogens is called adaptive immune response. Adaptive immunity is also referred to as acquired immunity or specific immunity and is only found in vertebrates. The adaptive immune response is specific to the pathogen presented. The adaptive immune response is meant to attack non-self pathogens but can sometimes make errors and attack itself. When this happens, autoimmune diseases can develop (e.g., lupus, rheumatoid arthritis). NURS 6051 wk 2: Adaptive Response Assignment
The hallmark of the adaptive immune system is clonal expansion of lymphocytes. Clonal expansion is the rapid increase of T and B lymphocytes from one or a few cells to millions. Each clone that originates from the original T or B lymphocyte has the same antigen receptor as the original and fights the same pathogen.
While the innate immune response is immediate, the adaptive immune response is not. However, the effect of the adaptive immune response is long-lasting, highly specific, and is sustained long-term by memory T cells.
“Change in all things is sweet” (Aristotle in Nicomachean Ethics, c. 350 BCE). Aristotle recognized that change in our world occurs naturally and can be both good and bad. Today, we recognize that adaptation is an essential physiological process by which our physiology changes in response to stressors of all sorts; some intrinsic and related to our natural life span, others environmental and related to the world in which we live, and still others that are self-inflicted and far too often destructive. Physiological adaptation can occur at different levels, from the molecular and subcellular level to whole cells, tissues, and organisms. It is now clear that many adaptive mechanisms evolved to enhance survival, but others provide no benefit or underlie disease conditions. NURS 6051 wk 2: Adaptive Response Assignment
In this issue of Physiology, a clear example of physiological adaptation at the integrated whole organism level is evident by the response of some large mammals to climate change. Similarly, our adaptive responses to changing levels of oxygen, particularly hypoxia, are crucial for survival. In another review in this issue, the molecular mechanisms linking oxygen sensing and apoptotic cell death are discussed in the context of adaptive responses. As is evident by this review, the mechanisms underlying physiological adaptation are complex. In recent years, we have learned that physiological adaptation can involve epigenetic modifications that are heritable changes in gene activity without modifications of the DNA sequence itself. Another review within this issue explores epigenetic alterations involved in chronic lung diseases. As pointed out in this and other previous articles published in Physiology, adaptive responses can be triggered by our own lifestyles. For example, obesity is a major human problem that is linked to adaptive and maladaptive changes across a number of physiological systems. Similarly, as discussed in another review within this issue, alcohol abuse can lead to maladaptations triggering a variety of associated diseases. It is clear that physiological adaptations are important in both health and disease, so our interest in understanding underlying mechanisms is well justified. We are only scratching the surface, and, lucky for us as scientists, there is so much more to learn.
Global warming is a fact of life, and we all should be concerned about how we will adapt to this changing world. If large mammals are to survive the hotter, drier habitats in a climate-changed future, they will have to rely on their ability to alter their physiology. Genetic adaptation to climate change is unlikely because large mammals reproduce slowly and are long-lived. Human-made barriers also will prevent them from moving to more suitable environments, and their large body size limits microhabitats available for thermal refuge. In their review (2), Fuller et al. discuss how large arid-zone mammals, such as goats, oryx and kangaroos, alter their behavior and physiology to buffer hotter and drier environments. Traditionally, such studies investigating physiological adaptation have relied on measurements made from animals housed under artificial laboratory conditions. Although these investigations have yielded valuable insights, they do not accurately predict how animals function in their natural environment. Stress responses with human observers nearby also confound normal physiological and behavioral responses of the animals. In their studies, Fuller and colleagues use data obtained by biologging in free-living mammals. A detailed understanding of free-living mammalian physiology, such as thermoregulatory behavior, body temperature variability, and selective brain cooling, is required to accurately predict future ecological patterns and conserve biodiversity. NURS 6051 wk 2: Adaptive Response Assignment.