The main difference between naive and memory B cells is that naive cells have not been exposed to an antigen before, whereas memory B cells have been previously activated by exposure to an antigen.
The immune system consists of different types of cells. Moreover, the most common types of cells among them are neutrophils, monocytes/macrophages, and lymphocytes (T cells, B cells, NK cells). The other components of the immune system include cytokines, antibodies, and complement proteins. The overall function of these cells and the immune system is to defend the body against infections and outside invaders.
Key Areas Covered
1. What are Naive Cells
– Definition, Exposure to Antigens, Features
2. What are Memory B Cells
– Definition, Exposure to Antigens, Features
3. Difference Between Naive and Memory B Cells
– Comparison of Key Differences
Key Terms
Naive Cells, Memory B Cells
What are Naive Cells
Naive cells are the cells of the immune system that has not yet encountered an antigen, a foreign substance that activates an immune response. Naive cells are also known as naive lymphocytes. There are two types of lymphocytes: T cells and B cells. The maturation of these lymphocytes happens in primary lymphoid organs. T cells mature in the thymus, while B cells mature in the bone marrow. Until these cells encounter an antigen-presenting cell (APC) and differentiate into effector cells, these cells are present as naive cells.
Naive cells are a type of white blood cell that plays a critical role in the immune system. They circulate continuously throughout the lymphatic vessels, blood, and peripheral tissues. While they circulate throughout the blood, they face antigen-presenting cells. If naive cells cannot recognize antigen-presenting cells by their receptors, naive cells re-enter the bloodstream, starting the process all over again. If they encounter an antigen while circulating through the body, naive cells activate into different types of T cells. Moreover, the activation of naive B cells and naive T cells occurs in secondary lymphoid organs like tonsils, lymph nodes, mucosal tissues, spleen, and Peyer’s patch. Upon the confrontation of the antigen, lymphocytes receive three types of signals, an antigen signal via TCR or BCR, a cytokine signal, and a co-simulatory signal. Then after receiving these signals, the cell is differentiated into an effector cell.
What are Memory B Cells
Memory B cell is a type of lymphocyte belonging to the adaptive immune system. Memory B cells remember the characteristics of the antigen that activated their parent cell B cell during the initial infection. When they confront the same antigen again, they activate a secondary immune response. Memory B cells have receptors on their cell membrane that are similar to their parent cell receptors. These receptors recognize and activate a specific antigen. These cells are developed within the germinal centers of the secondary lymphoid organs. Generally, these cells have a longer life span, sometimes extending up to 10 years. They remain circulating in the blood.
When these cells confront the antigen for the second time, they proliferate and differentiate into plasma cells. This differentiation process is fast, and then the secondary immune responses are made. The second time the cells encounter the same specific antigen, they produce more antigens, destroying the virus quickly.
Difference Between Naive and Memory B Cells
Definition
Naive cells are the cells of the immune system that has not yet encountered an antigen, while memory B cells are types of B lymphocytes that form a part of the adaptive immune system.
Exposure to Antigen
Naive cells have not been exposed to an antigen, whereas memory B cells have been previously activated by exposure to an antigen.
Cell Types
There are two types of naive cells; naive T cells and naive B cells, but there are no different types of memory B cells.
Life Span
Naive cells have a shorter life span, whereas memory B cells have a comparatively longer life span.
Affinity Maturation
The affinity of naive cells to the antigen is lower, whereas the affinity of memory B cells to an antigen is comparatively higher.
Conclusion
There are many types of cells in the immune system performing different functions. These cells are associated with the body’s defense mechanism. The main difference between naive and memory B cells is that naive cells have not been exposed to an antigen before, whereas memory B cells have been previously activated by exposure to an antigen.
Reference:
1. “B cell memory: building two walls of protection against pathogens.” Nature.com
2. “Components of the immune system.” Astro – Targeting Cancer Care.
Image Courtesy:
1. “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
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