As illustrated, T-helper lymphocytes play an important role in the regulation of both T and B cell responses as well as cytotoxic T-lymphocytes. However, the most important property of adaptive immunity is its capacity to establish an immunological memory response, assuring a stronger and faster protective immune response whenever challenged again by the same pathogen. While the primary immune response on average takes 10–14 days to build up, immunological memory shortens the immunological reaction time to a couple of days, thereby effectively preventing future reinfection with the same agent (Fig. 1).

Fig1. Dynamics of the adaptive immune response . Adapted from “Understanding Modern Vaccines: Perspectives in Vaccinology, Volume 1”, 2011 Elsevier, Oberdan, L., Cunningham, A., Stern, P.L.: Chapter2. Vaccine immunology ; p. 45

At the first encounter with an antigen usually only a small number of lymphocytes expressing a given antigen specificity are available. Upon activation by antigen recognition, T and B lymphocytes will go through rapid proliferation, leading to the accumulation of an increased number of cells expressing receptors for the specific antigen. Some of these cells will differentiate into effector cells while others will become “memory cells,” able to survive for longer periods of time within the host. Any exposure to an antigen ( pathogen or vaccine ) therefore leads to a long-term modification of the cellular repertoire, such that the relative frequency of T and B cells specific for an individual antigen is increased in antigen exposed individuals compared with naïve individuals [ 1 , 2 ]. Memory T and B cells will develop secondary (recall) responses on reencounter with their specific antigen. The adaptive response on secondary exposure leads to a rapid expansion and differentiation of memory T and B cells into effector cells, and the production of high levels of antibodies. A higher proportion of IgG and other isotypes of antibodies compared with the level of IgM characterizes memory antibody responses. During the process of reactivation the binding avidity of antibodies can be optimized by somatic hyper mutation of the variable antigen-binding region.

The capacity to generate immune memory is the key feature of the adaptive immune system and is crucial for maintenance of long-term protection. This capacity to establish an immunological memory response also is the fundamental basis for the biological effects of vaccines. Initially antigen processing and presentation by dendritic cells (DCs) are key steps that defi ne the environment and the course of efficient immune response s [ 3 ]. Therefore, innate immunity sets the scene for the subsequent adaptive response and innate and adaptive immunity have to interact vigorously in order to initiate the most effective type of protective immunity.

References
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[1] Gasper DJ, Tejera MM, Suresh M (2014) CD4 T-cell memory generation and maintenance. Crit Rev Immunol 34:121–146

[2] Takemori T, Kaji T, Takahashi Y et al (2014) Generation of memory B cells inside and outside germinal centers. Eur J Immunol 44:1258–1264

[3] Edwards KM, Decker MD (2008) Pertussis vaccines. In: Plotkin SA, Orenstein WA, Offit PA (eds) Vaccines, 5th edn. Elsevier, New York, pp 467–518

مواضيع ذات صلة

الحساسية الدوائية نحو العوامل المخصرة للوصل العَصَبِي العَضَلِي

آليات حساسية السلفوناميدات ومظاهرها

Antigen - Antibody Interaction: Specificity and Cross - Reactivity

ANTIBODY SYNTHESIS

Tolerance to Commensal Microbes and Fetal Antigens

B Lymphocyte Tolerance

Peripheral T Lymphocyte Tolerance

B Cells

T Cells

إزالَةُ التَحسس نحو البنسلين Penicillin Desensitization

الحساسية نحو البنسلين

الفرق بين فَرْطُ التحسس والحساسية الدوائية