What is the Difference Between Memory T Cells and Memory B Cells

The key difference between memory T cells and memory B cells is that memory T cells memorize previous antigens that activated their parent T cells and quickly convert to effector T cells when they recognize the antigen for the second time, while memory B cells memorize previous antigens that activated their parent B cells and mount a specific antibody response when they recognize them for the second time.

Immunological memory is a very important and unique property of the human immune system. It can store information about a stimulus and can mount a very effective response when the same stimulus is encountered for a second time. This response (a secondary response) is quicker and stronger than the primary response. Memory T cells and memory B cells are two types of immunological memory cells. T cells originate in the bone marrow and mature in the thymus. B cells originate and mature in the bone marrow.

CONTENTS

1. Overview and Key Difference
2. What are Memory T Cells 
3. What are Memory B Cells
4. Similarities – Memory T Cells and Memory B Cells
5. Memory T Cells vs Memory B Cells in Tabular Form
6. Summary – Memory T Cells vs Memory B Cells

What are Memory T Cells?

Memory T cells are a subset of T lymphocytes. They have some of the same functions as memory B cells. Their lineage is still unclear. It is believed that some of the effector T cells produce memory T cells. The primary function of memory cells is to augment the immune response after the reactivation of those cells when they are re-exposed to the same pathogen. Memory T cells usually reside in the tissue of the intestine, lungs, skin, and genital surfaces.

There are different memory T cells with different functions. Central memory T cells (T_CM) confer powerful immunity against viruses, bacteria, and cancer cells. Effector memory T cells (T_EM) are responsible for cytotoxic action against pathogens. Tissue-resident memory T cells (T_RM) are present in barrier tissues (epithelium) for longer periods of time. They are responsible for conferring quick responses to barrier breaches to any relevant pathogen present. Stem cell memory T cells (T_SCM) are capable of self-renewal and are also capable of generating both (T_CM) and (T_EM). Moreover, virtual memory T cells (T_VM) can produce various cytokines and involve in subduing unwanted immunological states. There are also speculations about their usage in treating autoimmune diseases.

What are Memory B Cells?

Memory B cells memorize previous antigens that activated their parent B cells and mount a specific antibody response when they recognize them for the second time. Memory B cell or plasma cell is a type of B lymphocyte that forms a part of the adaptive immune system. These cells are normally developed in the germinal centres of the secondary lymphoid organs. Memory B cells circulate in the bloodstream in a quiescent state for years.

Their primary function is to memorize the characteristics of the antigen that activated their parent B cell during primary infection. Later, if this antigen is encountered again, memory B cells trigger an accelerated and robust secondary immune response. Moreover, memory B cells have B cell receptors (BCRs) on their cell membrane like their parent B cells. This allows them to recognize antigens and mount secondary antibody responses pretty quickly. Furthermore, there are different types of memory B cells with different functions. Germinal centre independent memory B cells are less specialized to a specific antigen and, therefore, can recognize a wider range of antigens of pathogens. T-independent memory B cells produce IgM antibodies to help clear infections. T-bet memory B cells are important in immune responses against intracellular bacterial and viral infections.

What are the Similarities Between Memory T Cells and Memory B Cells?

• Memory T cells and memory B cells are two types of immunological memory cells.
• Both are involved in generating secondary immune reactions.
• They are capable of removing pathogens, such as viruses and bacteria, the body has been previously exposed to.
• Both are important parts of the adaptive immune system.
• T cells are sometimes needed for the development and activation of memory B cells.
• They are both extremely important for human survival.

What is the Difference Between Memory T Cells and Memory B Cells?

Memory T cells memorize previous antigens that activated their parent T cells and quickly convert to effector T cells when they recognize them for the second time, while memory B cells memorize previous antigens that activated their parent B cells and mount a specific antibody response when they recognize them for the second time. Thus, this is the key difference between memory T cells and memory B cells. Furthermore, memory T cells are a subset of T lymphocytes, while memory B cells are a subset of B lymphocytes.

The below infographic presents the differences between memory T cells and memory B cells in tabular form for side-by-side comparison.

Summary – Memory T Cells vs Memory B Cells

Memory T cells and memory B cells are two types of immunological memory cells. Both these memory cells are important parts of the adaptive immune system. They are generated in the bone marrow and the thymus. Memory T cells memorize previous antigens that activated their parent T cells and quickly transform into effector T cells when they recognize them for the second time. Memory B cells memorize previous antigens that activated their parent B cells and mount a specific antibody response when they recognize them for the second time. So, this is the key difference between memory T cells and memory B cells.

Reference:

1. “Memory T Cell.” An Overview | ScienceDirect Topics.
2. Kurosaki, Tomohiro, et al. “Memory B Cells.” Nature News, Nature Publishing Group, 13 Feb. 2015.

Image Courtesy:

1. “2218 Clonal Selection and Expansion of T Lymphocytes” By OpenStax College – Anatomy & Physiology: Connexions Web site. Jun 19, 2013. (CC BY 3.0) via Commons Wikimedia
2. “Original antigenic sin” By Original_antigenic_sin.png: User: DO11.10derivative work: Rehua (talk) – This file was derived from Original antigenic sin.png: (CC BY-SA 3.0) via Commons Wikimedia