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Ch. 16 - Adaptive Immunity
Bauman - Microbiology with Diseases by Taxonomy 6th Edition
Bauman6th EditionMicrobiology with Diseases by TaxonomyISBN: 9780134832302Not the one you use?Change textbook
Chapter 16, Problem 6

Which of the following lymphocytes predominates in blood?
a. T cells
b. B cells
c. Plasma cells
d. Memory cells
e. All are about equally prevalent

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1
Understand the types of lymphocytes listed: T cells, B cells, plasma cells, and memory cells. Each has a distinct role in the immune system.
Recall that plasma cells are differentiated B cells that produce antibodies and are usually found in tissues rather than circulating blood.
Memory cells are long-lived lymphocytes that remain after an infection to provide faster response upon re-exposure; they are a subset of T or B cells, not a separate predominant population.
Between T cells and B cells, consider which is more abundant in peripheral blood. T cells generally make up a larger proportion of circulating lymphocytes compared to B cells.
Conclude that the lymphocyte type that predominates in blood is the one with the highest relative percentage among circulating lymphocytes, which is typically T cells.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Types of Lymphocytes

Lymphocytes are white blood cells essential for immune responses, primarily including T cells, B cells, plasma cells, and memory cells. T cells help in cell-mediated immunity, B cells produce antibodies, plasma cells are differentiated B cells that secrete antibodies, and memory cells provide long-term immunity.
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Introduction to T Lymphocytes

Prevalence of Lymphocyte Types in Blood

In peripheral blood, T cells are the most abundant lymphocytes, typically making up about 60-70% of circulating lymphocytes. B cells are less common, plasma cells are rarely found in blood as they reside mainly in tissues, and memory cells are a subset of T or B cells, not a separate predominant population.
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Introduction to T Lymphocytes

Role of Plasma and Memory Cells

Plasma cells are terminally differentiated B cells that produce antibodies but are mostly located in bone marrow and lymphoid tissues, not blood. Memory cells are long-lived lymphocytes that respond quickly upon re-exposure to antigens, existing as subsets of T or B cells rather than a distinct major population in circulation.
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Naive B cells Become Effector (Plasma) Cells & Memory Cells