Germs and Your Immunity

Pathogens are microorganisms that can cause disease. To eliminate them, we have two types of immune responses: innate immunity and adaptive or acquired immunity.

The front line of immune function, innate immunity, provided immediate defense against pathogens. It includes anatomic barriers such as skin and mucous membranes, physiologic barriers such as temperature and pH, phagocytic cells such as neutrophils and macrophages, and inflammation. It is essential for its quick, nonspecific response time, but will not provide long lasting protection. Due to its nonspecific nature, innate immunity may also cause damage to the body, as in prolonged fevers or a chronic inflammatory response.

Adaptive immunity is acquired as the body creates immunological memories of encounters with pathogens. Unlike innate immunity, adaptive immunity elicits a specific response to the pathogen and it is diverse enough to fight different types of disease-causing microorganisms. Each time the body is faced with an antigen, adaptive immunity evolves to better combat it. This system will also prevent harm to the body and will not react against its own tissues. Immune cells and chemical mediators are part of the adaptive immune system. It is beneficial for long-term protection, but has a significantly lower response time than the innate immune system.

The two immune systems work together to rid the body of dangerous pathogens. Complement activation and cell surface receptors as part of innate immunity set the adaptive immune system up to regulate B and T cell responses. Both responses are incredibly important and are significantly more effective together than individually.

If we are faced with a pathogen (for example, the measles), the first line of defense will be our skin and mucous membrane. If measles virus passes these barriers, it will be faced with the phagocytes and a fever to try to kill it off. The adaptive immune system will jump in to learn more about the measles, sending antibodies to fight it. After recovering from the virus, a person is significantly less likely to be infected by it again, because their adaptive immune system has learned to combat it effectively.

Carroll, M. (2004). The complement system in regulation of adaptive immunity. Nature Immunology, 5(10), 981-986. http://dx.doi.org/10.1038/ni1113

Rodriguez, J. & Fischer, R. (2016). Introduction to the Human Immune System (1st ed., pp. 14-17,34,36). Retrieved from https://webcampus.uws.edu/pluginfile.php/121810/mod_resource/content/2/Week%201%20Introduction%20to%20the%20Immune%20System%20-%20one%20slide%20per%20page.pdf