Sexually transmitted diseases
Frank J. Dye in Human Life Before Birth, 2019
Our immune system, in general, is composed of two types of cells: B lymphocytes (B cells) and T lymphocytes (T cells). B cells make antibodies to protect us by means of what is called humoral immunity. T cells aggressively destroy foreign germs and home-grown cancer cells and, in addition, orchestrate the response of the immune system to an onslaught of infectious agents. There are various kinds of T cells according to their role in the immune defense system. One kind of T cell important in the regulation of the immune system is the CD4 T cell. This is precisely the type of cell infected by the HIV virus. By destroying these CD4 cells, the HIV virus weakens our immune system and, although this does not kill people directly, it makes people vulnerable to potentially fatal infections and cancers.
Dermal Hypersensitivity: Immunologic Principles and Current Methods of Assessment
David W. Hobson in Dermal and Ocular Toxicology, 2020
The two major arms of the immune system are humoral immunity and cell-mediated immunity. Specific antibodies from B lymphocytes mediate humoral immunity, whereas specifically sensitized T lymphocytes produce cell-mediated immunity. Various cells (macrophages) in the mononuclear phagocytic system (MPS) process and present antigens on their surface membranes in context with class II major histocompatibility (MHC) antigens. These antigen-presenting cells enable specific lymphocytes to recognize the foreign antigen and to generate an immune response against the antigenic substance. The cell in the skin with this antigen presentation role is primarily the Langerhans’ cell.25 T lymphocytes function as two main subpopulations which express different surface markers, the helper/effector T cells (TH) and the suppressor T cells (Ts). Human TH cells express CD4+ and Ts cells express CD8+ surface antigens.17
COVID-19
Stephen T. Sinatra, Mark C. Houston in Nutritional and Integrative Strategies in Cardiovascular Medicine, 2022
Immunity involves a partnership of memory B- and T-cells. B-cells are responsible for humoral immunity which produces specific antibodies to the virus. However, T-cells are an important component to the immune system. T-cells respond directly to the virus in a form of cell-mediated immunity.31 CD4+ and CD8+ T-cells show a response to COVID-19 in 100% and 70% of convalescent COVID patients, respectively. T-cell responses target the spike, M, N, and other ORFs.31 T-cell reactivity to SARS-CoV-2 epitopes is also detected in approximately 50% of non-exposed individuals.31 Tests to measure T-cell reactivity are not routinely available. However, both the B-cell and T-cell arms of the immune system contain memory cells which activate within minutes of exposure to the virus, even after detectable levels are not evident. Mild COVID-19 may elicit strong T-cell responses in the absence of detectable virus-specific antibodies. Scientists see signs of lasting immunity to COVID-19, even after mild infections. Approximately 50% of patients who have had colds (coronavirus) have T-cells active against COVID-19.31 100% of patients who recover have T-cells active against COVID-19.31 The T-cell arm of the immune system contributes to herd immunity (Figure 15.3).
Lower proportion of CD19+IL-10+ and CD19+CD24+CD27+ but not CD1d+CD5+CD19+CD24+CD27+ IL-10+ B cells in children with autoimmune thyroid diseases
Published in Autoimmunity, 2020
Karolina Stożek, Kamil Grubczak, Viviana Marolda, Andrzej Eljaszewicz, Marcin Moniuszko, Artur Bossowski
Focussing our attention on the family of B lymphocytes, the variety of their functions includes production of antibodies, antigen-presenting capacity and release of cytokines [14]. Promotion of inflammatory response constitutes the primary role of B-cells in humans. Traditionally, B-cells are responsible for humoral immunity via antigen-specific antibody production. Their other positive features include the regulation of CD8+ T cell responses, functioning of dendritic cells, inducing T cell activation or organization of lymphoid tissue. In the last decades intensified studies have brought a completely opposite view on their additional role. There are well supported proofs that B-cells are able to regulate immune responses in a negative way through the secretion of anti-inflammatory cytokines. Thus, B cells are considered to have both positive and negative regulatory roles in immunity [15–17].
Immunogenicity and protection efficacy of enhanced fitness recombinant Salmonella Typhi monovalent and bivalent vaccine strains against acute toxoplasmosis
Published in Pathogens and Global Health, 2021
Fei-Kean Loh, Sheila Nathan, Sek-Chuen Chow, Chee-Mun Fang
B cells are the hallmark of humoral immunity for their ability to secrete specific antibodies that can neutralize the antigens. Among the antibody subtypes, IgG antibodies have been found to opsonise T. gondii for phagocytosis and inhibit parasite binding to the host cell receptors [54]. The low IgG titers detected in CVD910 vector control proved that S. Typhi live vector and recombinant T. gondii antigen booster has limited contribution in enhancing IgG production. Furthermore, low IgG titers were detected in the mouse group receiving monovalent CVD910-GRA2. Hence, the strong T. gondii-specific humoral immunity in CVD910-GS group is most likely contributed by the immunogenic B cell epitopes present in the SAG1 antigen. In complement, the mice immunized with peptide containing B-cell epitopes of SAG1 (amino acids 301–320) had shown to produce high titers of IgG [55,56].
Immunopathological and molecular basis of functional dyspepsia and current therapeutic approaches
Published in Expert Review of Clinical Immunology, 2018
Mounika Addula, Victoria E. D. Wilson, Savio Reddymasu, Devendra K. Agrawal
Consideration of basic forms of complex normal immunology of the gut is a useful prelude to further examination of immune dysregulation theories germane to FD. Immunity in humans can be broadly classified into innate and acquired (adaptive) immunity. The components of innate immunity include physical barriers, chemical barriers, natural killer cells, plasma proteins, dendritic cells, and others. Acquired immunity can further be classified into humoral immunity (mediated by B-lymphocytes and plasma cells which produce antibodies) and cell-mediated immunity (mediated by T cells such as T helper cells and cytotoxic cells). Mucosa of the epithelium host major immunological responses. Gut associated lymphoid tissue (GALT) and draining lymph nodes foster adaptive immune responses. Intestinal epithelium contains many T cells, whereas lamina propria contains B cells, T cells, macrophages, eosinophils, mast cells, etc. Any alteration in the mucosal normality – whether due to bacteria, food antigens, allergens, and other factors – can trigger release of pro-inflammatory mediators such as IL-8, MCP1, TNF-α, RANTES, IL-6. These stimulate neutrophils, B-cells, T cells, eosinophils, and macrophages that further mediate the inflammatory process (Figure 1). Dendritic cells help present antigens during this process. Findings from several pertinent studies indicate robust immune mechanisms underneath pathophysiology in FD associated with close intricate nature of both types of immune responses which makes it difficult to accurately delineate between innate and acquired pathophysiological basis of the disease.
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