This set of Immunology Multiple Choice Questions & Answers (MCQs) focuses on “Development of B1 and Marginal Zone B-cells”.
1. Where is the population of B1 cells present?
a) Thymus
b) Lymph nodes
c) Intestinal tract
d) Spleen
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Explanation: B1 cells are present in the peritoneal and pleural cavities. These cavities are present in areas near and around the lungs as well as intestinal tract. They show their response to foreign proteins, called antigens and also to some of the body’s own antigens. B2 cells, on the other hand, contribute to make up the large portion of the white blood cells (WBCs) in the body. They mainly circulate in the blood and in the lymphoid system which include organs such as the thymus, spleen, lymph nodes, and bone marrow.
2. B1 cells are already present in new-borns and play an important role in natural immunity?
a) True
b) False
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Explanation: B1 cells are present in majority of all B lymphocytes in new-borns but in adults the proportion of B1 cells in adults is comparatively less. This is one of the main reasons why B1 cells are considered carriers of natural immunity i.e., the innate immune system because they are naturally present since birth in new-borns. On the other hand, B2 cells are mainly associated with adaptive immune system.
3. Marginal zone B1 cells are characterised by which type of response?
a) T-dependent antigenic response
b) T-independent antigenic response
c) B-dependent antigenic response
d) B-independent antigenic response
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Explanation: B-cells that develop in the bone marrow are tracked into functional subsets in the spleen, including marginal zone (MZ) B-cells. MZ B-cells are mainly characterized by T-independent antigenic responses and they require the elaboration of gene expression programs for development.
4. Which of the following is NOT the homing receptor of MZ B cells of mice?
a) S1P1
b) S1P3
c) CXCR5
d) NBH cells
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Explanation: Mice MZ B cells show the presence of 5 major homing receptors namely S1P1, S1P3, CXCR5, αLβ2 integrin and α4β1 integrin. Their phenotype is IgMhi IgDlow CD21hi CD23– CD1dhi and they are located in the spleen. These cells mainly respond to T-cell-dependent responses and show great production affinity towards IgG1 antibodies. They also associate with T-cell-independent responses and during such a response they show greater affinity to IgM, IgG2b, IgG3 and IgA. MZ B cells of mice are non-mutated and polyreactive.
5. In humans, where are MZ B cells located?
a) Lymph nodes
b) Spleen
c) Bone marrow
d) Liver
View Answer
Explanation: In humans, MZ B cells are located in various parts of the body including the inner wall of lymph nodes, the epithelium of tonsils and the subepithelial area of mucosa-associated lymphoid tissues as well as in some areas of intestinal Peyer’s patches. On the other hand, in mice, MZ B cells are present in spleen.
6. MZ B cells differentiate in which type of cells?
a) Lymphoblast
b) Macrophages
c) Plasmablasts
d) B1 cells
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Explanation: MZ B cells differentiate into plasmablasts once they interact with antigens associated with macrophages or neutrophils. These plasmablasts produce large amounts of IgM antibody isotype. Along with IgM, MZ B cells also produce IgG and IgA by the mechanisms of class-switch recombination (CSR).
7. Patients that lack the spleen do NOT result in which of the following risks?
a) Pneumonitis
b) Meningitis
c) Fulminant septic syndrome
d) Slipped disc
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Explanation: Patients can lack the presence of spleen because of the reasons like surgery or congenital asplenia. Due to such reasons, they can be at a higher risk of pneumonitis, meningitis and fulminant septic syndrome. These risk factors can be caused if they ever come in contact with capsulated bacteria like Streptococcus pneumoniae, Haemophilus influenzae and Neisseria meningitidis. These infections generally result due to improper functioning of MZ B cells.
8. Signals from which type of receptor contribute to development of MZ B cells?
a) BCRs
b) TCRs
c) TLRs
d) APRs
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Explanation: Signals from TLRs may contribute to the development of human MZ B cells. TLR ligands can promote the differentiation of transitional B cells into MZ-like B cells, and patients with defective TLR signalling have reduced numbers of MZ B cells. However, this reduction may reflect a central role of TLRs in providing survival signals rather than differentiation signals to MZ B cells.
9. What is the phenotype of Human MZ B cells?
a) IgMhi IgDlow CD1c+ CD21hi CD23– CD27+
b) IgGhi IgMlow CD1c– CD21low CD23+ CD27–
c) IgMlow IgDhi CD1c+ CD21hi CD23– CD27+
d) IgMhi IgDlow CD21hi CD23– CD1dhi
View Answer
Explanation: The phenotype of human MZ B cells is IgMhi IgDlow CD1c+ CD21hi CD23– CD27+. These cells are mutated, monoreactive and in some cases they also act as polyreactive. They are confined to subcapsular sinus in lymph nodes, tonsillar epithelium and subepithelial dome of Peyer’s patches. These cells develop mainly in fetal liver, mesenteric lymph nodes as well as in postnatal spleen.
10. T2B cells are precursors of which animal?
a) Human
b) Shark
c) Mice
d) Chick
View Answer
Explanation: T2B and some T1B cells are considered to be as the precursors of MZ B cells associated with mice. MZ B cells of the mice are non-mutated and polyreactive. They develop in the postnatal spleen and therefore are localized in the spleen itself. Hence these cells are also named as splenic MZ B cells.
Sanfoundry Global Education & Learning Series – Immunology.
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