Immune Responses: Primary and Secondary Alexander A Ademokun, King's College London School of Medicine, London, UK Deborah DunnWalters, King's College London School of Medicine, London, UK
Email a friend Contact the editor about this article How to cite
Published online: September 2010 DOI: 10.1002/9780470015902.a0000947.pub2
Full Article on Wiley Online Library Abstract
Images
References
Abstract Immune responses to antigens may be categorised as primary or secondary responses. The primary immune response of the body to antigen occurs on the first occasion it is encountered. Depending on the nature of the antigen and the site of entry this response can take up to 14 days to resolve and leads to the generation of memory cells with a high specificity for the inducing antigen. The humoral response, mediated by B cells with the help of T cells, produces highaffinity and antigenspecific antibodies. This is in contrast with the CD8 Tcell response which leads to the generation of large numbers of antigenspecific cells that are capable of directly killing infected cells. Antigenspecific CD4 T cells, which provide help to B cells in the form of cytokines and other stimulatory factors, can also be expanded upon antigenic stimulation. The secondary response of both B and T cells is observed following subsequent encounter with the same antigen and is more rapid leading to the activation of previously generated memory cells. This has some quantitative and qualitative differences from the primary response. Key Concepts: The innate immune system is the first line of defence against infectious agents. When this is breached, the adaptive immune system provides a more efficient response to clearing pathogens. The adaptive immune system has the capacity to ‘remember’ previous antigens, a process termed immunological memory. Antigenspecific T cells are selected during a primary immune response and expand to produce clones of T cells with high specificity for the activating antigen. In a B cell primary response to a thymusdependent antigen, the immune system selects B cells with a high affinity and specificity for the antigen and these become memory cells. The selection of B cells with a high affinity for a given antigen occurs in the germinal centres of secondary lymphoid follicles and requires the enzyme activationinduced cytidine deaminase (AID) and interactions with other immune cells. The ability to change the isotype of antibody produced (class switching) by a B cell also occurs in germinal centres and requires AID. In a secondary response to the same antigen, memory cells are rapidly activated. This process is quicker and more effective than the primary response. Keywords: antigens; memory cells; clonal expansion; germinal centres; affinity maturation; class switching
Related Sub-Topics: Innate Immunity | Acquired (Adaptive) Immunity
Sign up for e-alerts
THEMES Essentials in Biochemistry Soil Climate Change Biology Vaccination Obesity Stem Cells More Themes >
|
View Related Sites
Search eLS
Tansley reviews Read the latest Tansley reviews from New Phytologist
Feeling overwhelmed? Wasting time scanning endless search results for the right article? Refine your search, use eLS. Watch the Video
Learn more about eLS Find out how eLS can help you select and research topics in the life sciences. Take the Tutorial
Join us on Twitter Follow tweets on recent articles @eLifeSciences. Follow
Immune Responses: Primary and Secondary - Encyclopedia of Life ...
About Wiley
Enter keyword(s)
Immune Responses: Primary and Secondary Alexander A Ademokun, King's College London School of Medicine, London, UK Debo...
