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What triggers class switching?

Author

Olivia House

Updated on February 25, 2026

What triggers class switching?

Class switching occurs after activation of a mature B cell via its membrane-bound antibody molecule (or B cell receptor) to generate the different classes of antibody, all with the same variable domains as the original antibody generated in the immature B cell during the process of V(D)J recombination, but possessing

In this regard, where does class switching happen?

Class switching is a process which takes place in B cells to alter the class of antibody produced during an immune response from IgM to one of the other classes.

Furthermore, what causes isotype switch to IgE? Interleukin 4 causes isotype switching to IgE in T cell-stimulated clonal B cell cultures. J Exp Med. 1988 Sep 1;168(3):853-62.

Consequently, which cytokine causes class switching to IgE?

In order for a B lymphocyte to switch to IgE production it needs two signals provided by a Th2 cell in the form of the cytokines interleukin (IL-) 4/IL-13 and ligation of the CD40.

Which cytokine stimulates isotype switching from IgM to IgA?

Isotype switching is preceded by transcriptional activation of the isotype in question (Chapter 4). Two major cytokines, IL-4 and TGF-β, induce surface IgM-positive (sIgM+) B cells to switch to downstream isotypes, including IgE and IgA (Fig. 19.7).

Is class switching reversible?

Therefore, class switches are irreversible and must proceed from upstream classes to downstream classes, according to the order of the IGH constant region loci on the chromosome, which is shown in Figure 1—figure supplement 3.Aug 2, 2016

What are switch regions?

Switch regions are located at the 5′ position of each set of heavy-chain constant genes, except for the d gene, which accounts for the simultaneous expression of IgM and IgD on mature B cells. They are designated as Sm, Sgl to Sg4, Sal, Sa2, and Se, according to the flanking isotype.

What part of antibody determines class?

Antibody classes differ in valency as a result of different numbers of Y-like units (monomers) that join to form the complete protein. For example, in humans, functioning IgM antibodies have five Y-shaped units (pentamer) containing a total of 10 light chains, 10 heavy chains and 10 antigen-binding.

What causes somatic hypermutation?

Somatic hypermutation involves a programmed process of mutation affecting the variable regions of immunoglobulin genes. Unlike germline mutation, SHM affects only an organism's individual immune cells, and the mutations are not transmitted to the organism's offspring.

Do antibodies change DNA?

When a B cell switches from making IgM and IgD to one of the secondary classes of antibody, an irreversible change at the DNA level occurs—a process called class switch recombination.

What is switch recombination?

Definition. Class switch recombination is a process by which proliferating B cells rearrange the constant region genes in the immunoglobulin heavy chain locus to switch from expressing one class of immunoglobulin (such as IgM) to another (such as IgG).

What cytokine stimulates class switching to IgG?

Overall, these results revealed that IL-4 and IL-21 induce isotype switching in CD40L-stimulated human naive B cells to IgG at a comparable rate and that the combination of these cytokines has a synergistic outcome on this event.Aug 1, 2008

When does class switching occur in B cells?

Also, we do not extensively review all the information available about AID, as this protein is extensively discussed in the Scharff article (15) and in several other reviews (16–19). B cells undergo antibody, or Ig, class switching in vivo after immunization or infection or upon appropriate activation in culture.

How does IgM switch to IgG?

Antibody-producing cells undergo a process of differentiation and class switch recombination (CSR) such that the antibodies produced start as immunoglobulin M (IgM) and then switch to IgG and IgA as the concentration of antigen changes and as the cells differentiate.Oct 24, 2006

Which factors is critical for IgE isotype switching?

Three steps are crucial to mount an IgE immune response: 1) differentiation of dendritic cells that 2) promote the formation of allergenâ€specific Thelper type 2 lymphocyte which 3) subsequently induce the differentiation of B lymphocytes to IgE isotype switch.Jul 8, 2009

What are class switched memory B cells?

Class switching allows memory B cells to secrete different types of antibodies in future immune responses. The B cells then either differentiate into plasma cells, germinal center B cells, or memory B cells depending on the expressed transcription factors.

How do cytokines stimulate B lymphocytes?

TH cells activate B cells by their products, cytokines such as IL-4, IL-5, and IL-6, and membrane-bound stimulatory molecules including CD40 ligand. Each cytokine has pleiotropic activity on B cells and other cell types, and acts through a specific receptor.

What cytokine produces IgG?

Interleukin 6 (IL-6) is a multifunctional cytokine that is produced in a variety of clinical situations associated with inflammation. IL-6 was originally isolated and cloned as a B-cell differentiation factor that induced terminal B-cell differentiation and supported the production of immunoglobulin G (IgG).Jun 10, 2010

Do cytokines activate macrophages?

Macrophages activated by contact with pathogens or danger signals release cytokines and chemokines as a major component of the innate immune response (1). Inflammatory cytokines recruit other immune cells and orchestrate the actions and fates of the cells secreting them and those in the surrounding milieu.Oct 27, 2014

Which region of an immunoglobulin molecule determines its class?

The constant region determines the mechanism used to destroy antigen. Antibodies are divided into five major classes, IgM, IgG, Iga, IgD, and IgE, based on their constant region structure and immune function. The variable region is further subdivided into hypervariable (HV) and framework (FR) regions.

Can plasma cells class switch?

This occurs within the first few days of exposure to a novel antigen. Then, once a week or more has gone by, germinal centers form in secondary lymphoid organs, resulting in the production of class-switched, affinity-matured memory cells and plasma cells.

When does affinity maturation occur?

Affinity maturation occurs within the GC, where somatically mutated BCRs undergo selection on antigen retained on FDCs [39,40]. Antigen is retained in the form of ICs and involves the interaction of both complement receptors and FcγRIIB with these ICs on FDCs.

How does B cells get activated?

B cells are activated when their B cell receptor (BCR) binds to either soluble or membrane bound antigen. This activates the BCR to form microclusters and trigger downstream signalling cascades. Cytokines produced by T cells and other cells are important in determining what isotype the B cells express.

Why is IgM the first antibody produced?

IgM is the first antibody to be produced in response to infection since it does not require 'class switch' to another antibody class. However, it is only synthesized as long as antigen remains present because there are no memory cells for IgM.

What is IgM?

Immunoglobulin M (IgM), which is found mainly in the blood and lymph fluid, is the first antibody to be made by the body to fight a new infection. Immunoglobulin E (IgE), which is associated mainly with allergic reactions (when the immune system overreacts to environmental antigens such as pollen or pet dander).

Why do plasma cells migrate to bone marrow?

2.4 Maintenance of Plasma Cells

After leaving secondary lymphoid organs, plasmablasts, the dividing antibody-secreting cells, circulate in blood and migrate to bone marrow where they are exposed to survival factors necessary to further differentiate into long-lived plasma cells (Radbruch et al., 2006).

Does IgM Opsonize?

Antibody mediated opsonization

Phagocytic cells do not have an Fc receptor for immunoglobulin M (IgM), making IgM ineffective in assisting phagocytosis alone. However, IgM is extremely efficient at activating complement and is, therefore, considered an opsonin.

What is aid in immunology?

Activation-induced cytidine deaminase (AID), primarily expressed in activated mature B lymphocytes in germinal centers, is the key factor in adaptive immune response against foreign antigens.

Where does clonal selection occur?

This activation occurs in secondary lymphoid organs such as the spleen and the lymph nodes. In short, the theory is an explanation of the mechanism for the generation of diversity of antibody specificity.

What is IgA class switching?

IgA class switching is the process whereby B cells acquire the expression of IgA, the most abundant antibody isotype in mucosal secretions. IgA class switching occurs via both T-cell-dependent and T-cell-independent pathways, and the antibody targets both pathogenic and commensal microorganisms.

Do cytokines activate T cells?

The release of cytokines is centrally important to many aspects of T cell function. IL-1 is involved in T cell activation. IL-2 is a potent T cell growth factor which is essential for the long-term proliferation of activated T cells.

Which cytokine is not involved in B cell development and function?

In humans, mutations to the IL-7Rα gene result in SCID (Severe Combined Immune Deficiency), making IL-7 indispensable for T cell development; yet SCID patients have normal B cell populations [42]. Therefore, while IL-7 is not strictly required for the development of normal human B cells.

What are cytokines produced by?

Cytokines are mainly produced by macrophages and lymphocytes, although they can also be produced by polymorphonuclear leukocytes (PMN), endothelial and epithelial cells, adipocytes, and connective tissue. Cytokines are essential to the functions of macrophages.Oct 7, 2014

Which antibody is first produced in response to an antigen?

IgM is the first antibody secreted by the adaptive immune system in response to a foreign antigen. Monomeric IgM is a heterotetramer of approximately 180 kDa. However, the secreted form of IgM exists predominantly in a pentameric configuration with a molecular weight greater than 900 kDa.Jan 2, 2021

What produce plasma cells?

Plasma cells develop from B lymphocytes (B cells), a type of white blood cell that is made in the bone marrow. Normally, when bacteria or viruses enter the body, some of the B cells will change into plasma cells. The plasma cells make antibodies to fight bacteria and viruses, to stop infection and disease.

What cytokines do B cells produce?

Regulatory B cells (Breg) are distinguished by their ability to secrete IL-10 or TGFβ-1, while effector B cell populations produce cytokines such as IL-2, IL-4, TNFα, IL-6 (Be-2 cells) or IFNγ, IL-12 and TNFα (Be-1 cells).Apr 15, 2008

What is synergy in cytokines?

'Synergy by independent action' occurs when two cytokines induce distinctive sets of host response genes whose combined effector functions synergistically inhibit viral replication.May 18, 2013

What is the role of interleukin 2?

Interleukin-2 is made by a type of T lymphocyte. It increases the growth and activity of other T lymphocytes and B lymphocytes, and affects the development of the immune system.

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