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Frage | Antworten |
What are the central cells of adaptive immunity? | Lymphocytes bearing antigen receptors, which are responsible for its characteristic properties of diversity, specificity, and memory. |
What proportion of circulating leukocytes do lymphocytes constitute? Contrastingly, what proportion of lymph cells do they constitute? | Lymphocytes make up 20-40% of the body's leukocytes, and 99% of the cells in lymph. |
Roughly how many lymphocytes are there in the body? | ~10^12 (a trillion) |
What are the three broad subdivisions of lymphocytic cells? | B lymphocytes, T lymphocytes, and natural killer cells. |
Which lymphocytes are involved in cell-mediated immunity? | T lymphocytes |
Which lymphocytes are involved in humoral immunity? | B lymphocytes |
Which two cell types can B cells mature into? | Plasma and memory B cells. |
Which four cell types can naive T lymphocytes mature into? | T regulatory, T cytotoxic, T helper, and memory T cells. |
What is the main function of plasma B cells? | To secrete antibody. |
What is the main function of B memory cells? | To react quickly and specifically to an antigen next time it is encountered by the memory B cells. |
When do naive B and T lymphocytes mature? | When they are stimulated by interaction with antigen. |
Where are most lymphocytes activated? | In the lymph nodes, where they proliferate and mature into effector cells. |
Describe an unprimed/naive T/B cell. | Small (~6μm diameter), motile, nonphagocytic cells which cannot be differentiated from one another morphologically. Their cytoplasm forms a barely discernible ring around their nuclei, they have densely packed chromatin, few mitochondria, and a poorly developed endoplasmic reticulum and Golgi apparatus. The naive lymphocyte is generally thought to have a short life span. |
In their inactivated state, which cell cycle phase do B and T lymphocytes remain in? | G0. |
What do naive T/B cells differentiate into initially, when first interacting with antigen? | Lymphoblasts, 15μm diameter cells with a higher cytoplasm-to-nucleus ratio and more organellar complexity than small lymphocytes. |
Memory cells look like small lymphocytes. How can they be distinguished? | By the presence or absence of certain molecules on their cell membranes. |
How can B and T cells be distinguished down an electron microscope? | B cells look 'hairy' because of their IgD receptors, whereas T cells look much smoother. |
What is the main mechanism for differentiating B and T cells, as well as differentiating the many cells in the different lineages and maturational stages of lymphocytes? | Recognition by monoclonal antibodies. All of the monoclonal antibodies (those specific for a single epitope of an antigen) that react wit a particular membrane molecule are grouped together as a cluster of differentiation (CD). Around 250 CD markers have been described for human lymphocytes. |
Which type of T lymphocyte is a CD4+ lymphocyte? | A T-helper lymphocyte. |
Which type of T lymphocyte is a CD8+ lymphocyte? | A T-cytotoxic lymphocyte. Variably, natural killer cells can possess CD8+ antigenic epitopes. |
Which type of lymphocyte possesses CD21 antigenic epitopes on its cell membrane? | B lymphocytes |
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