What Is The Role Of Memory Cells – B lymphocytes are cells of the immune system that make antibodies to attack pathogens like viruses. They form memory cells that remember the same pathogen for faster antibody production in future infections.

In immunology, memory B cells (MBC) are a type of B lymphocyte that is part of the adaptive immune system. These cells develop in the germinal cter of secondary lymphoid organs. Memory B cells circulate in the bloodstream in a quiescent state, sometimes for decades.

What Is The Role Of Memory Cells

What Is The Role Of Memory Cells

Its function is to remember the characteristics of the antig that activated the B cell during the initial infection, so that if the memory B cell later fights the same antig, it will trigger a faster and stronger secondary immune response.

B Cell Memory: Building Two Walls Of Protection Against Pathogens

Memory B cells have a B cell receptor (BCR) on the cell membrane, identical to the cell division, which allows them to recognize antigens and mount a specific antibody response.

In the T cell depdt development pathway, naive follicular B cells are activated by antig presting follicular T helper B cells (T).

Naive B cells circulate through follicles in secondary lymphoid organs (i.e. spleen and lymph nodes) that can be activated by floating foreign peptides carried by the lymph or by antig presting cells (APCs) such as dendritic cells (DCs). .

B cells can also be activated by binding to foreign antigens at the periphery where they migrate to secondary lymphoid organs.

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The signal transduced by the binding of the peptide to the B cell causes the cell to migrate to the edge of the follicle bordering the T cell area.

B cells internalize the foreign peptide, cleave it, and express it in major histocompatibility complex class II (MHCII), a cell surface protein. In secondary lymphoid organs, most of the B cells will form B cell follicles where the germinal cell will form. Most B cells will differentiate into plasma cells or memory B cells in the germinal cell.

TFHs that express T cell receptors (TCRs) cognate to peptides (ie specific for the peptide-MHCII complex) at the border of the B cell follicle and the T cell zone will bind to the MHCII ligand. T cells will express the ligand molecule CD40 (CD40L) and will begin to produce cytokines that cause B cells to proliferate and undergo class switch recombination, a mutation in the genetic code of B cells that changes the type of immunoglobulin.

What Is The Role Of Memory Cells

B cells can differentiate into plasma cells, Cter B germ cells, or memory B cells depending on transcription factors. Activated B cells that express the transcription factor Bcl-6 will form B cell follicles and undergo a germinal cter reaction.

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After entering the germinal cell, B cells undergo proliferation, followed by mutation of the BCR genetic coding region, a process known as somatic hypermutation.

These mutations will increase or decrease the affinity of surface receptors for specific antigens, which is called affinity maturation. After acquiring the mutation, the receptor on the surface of the B cell (B cell receptor) is tested in the germinal cell for affinity with antig currt.

B cell clones with mutations that increase surface receptor affinity receive survival signals through interactions with the same TFH cells.

B cells that do not have a high affinity to receive this survival signal, as well as auto-reactive B cells, will be selected and die through apoptosis.

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These processes increase the variation in antigen binding sites, so that each newly developed B cell has a unique receptor.

After differentiation, memory B cells move to the periphery of the body where they will be better able to fight antig in evt from winter light.

Many circulating B cells are concentrated in areas of the body that have a high probability of contact with antigens, such as Peyer’s patches.

What Is The Role Of Memory Cells

Another hypothesis proposes that the transcription factor NF-κB and the cytokine IL-24 are involved in the process of differentiation into memory B cells.

Primary And Secondary Responses

An additional hypothesis states that B cells with relatively lower affinity for antig will become memory B cells, as opposed to B cells with higher affinity which will become plasma cells.

Not all B cells in the body undergo somatic hypermutation. IgM+ memory B cells that have not undergone class switch recombination indicate that memory B cells can be produced indepdtly from the germinal cter.

When infected with a pathogen, many B cells will differentiate into plasma cells, also called effector B cells, which produce the first wave of protective antibodies and help clear the infection.

Plasma cells release antibodies specific for the pathogen but fail to respond upon secondary exposure. The fraction of B cells with cognate BCRs to antig differentiate into long-term memory B cells in the body.

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Memory B cells can maintain BCR expression and will be able to respond rapidly upon secondary exposure.

Memory B cells produced during the primary immune response are specific for the antig present during the first exposure. In the secondary response, memory B cells specific to the antig or similar antig will respond.

When memory B cells express a specific antig, they proliferate and differentiate into plasma cells, which respond to and remove the antig.

What Is The Role Of Memory Cells

Memory B cells that are undifferentiated into plasma cells at this point can regress the germinal cter to undergo further class changes or somatic hypermutation for further affinity maturation.

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Differentiation of memory B cells into plasma cells is faster than differentiation of naïve B cells, which allows memory B cells to mount a more efficient secondary immune response.

The efficiency and accumulation of memory B cell responses is the basis for vaccines and booster shots.

Memory cell fotypes that predict the fate of plasma cells or germinal cter cells have been discovered a few years ago. Based on the expression microarray comparison between memory B cells and naive B cells, it was identified that there are some surface proteins, such as CD80, PD-L2 and CD73 that are only expressed in memory B cells, so they were also used for this division. cells in multiple phototypic subsets.

In addition, it has been shown that memory cells expressing CD80, PD-L2 and CD73 are more likely to be plasma cells. On the other hand, cells that lack this type of marker are more likely to form germinal cter cells. IgM

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Memory B cells can survive for decades, which gives them the capacity to respond to multiple exposures to the same antigen.

Their prolonged survival is thought to be the result of specific anti-apoptotic genes that are more expressed in memory B cells than in other B cell subsets.

In addition, memory B cells do not need constant interaction with antigens or with T cells for long-term survival.

What Is The Role Of Memory Cells

However, the actual lifespan of individual memory B cells remains poorly defined, despite their critical role in long-term immunity. In a study using the B cell receptor (BCR) transgenic system (which is an H chain transgenic mouse model that lacks secreted Ig, thus does not store immune complexes containing Ag), it was shown that the number of memory B cells. remains constant for a period of about 8-20 weeks after immunization. It is also estimated that the half-life of memory B cells is between 8-10 weeks, after conducting experiments in which the cells were treated in vivo with bromodeoxyuridine.

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In other experiments in mice, it has been shown that the lifespan of memory B cells is at least 9 times greater than the lifespan of follicular naive B cells.

Memory B cells are usually differentiated by the cell surface marker CD27, although some subsets do not express CD27. CD27-deficient memory B cells are associated with exhausted B cells or certain autoimmune conditions such as HIV, lupus, or rheumatoid arthritis.

Because B cells usually undergo class switching, B cells can express several immunoglobulin molecules. Some specific attributes of certain immunoglobulin molecules are described below:

It is important to mtion the importance of the integration of signaling pathways related to recepetors of BCRs and TLRs in order to modulate the production of antibodies by the expansion of memory B cells. Therefore, there are various factors that provide information for the secretion of different types of antibodies. It has been shown that the production of specific-IgG1, anaphylaxis-IgG1 and total-IgE depds in the signal produced by TLR2 and Myd88. In addition, the signal generated by TLR4 stimulated by natterin (a protein obtained from T. nattereri fish vom) accelerates the synthesis of IgE antibodies that act as an adjuvant, as shown in in vivo experiments with mice.

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The CCR6 receptor is a marker of B cells that will differentiate into MBC. These receptors detect chemokines, which are chemical messages that allow B cells to move around the body. Memory B cells can have this receptor so they can leave the germinal cell

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