Cellular I mmunology | MCQ Quiz | OmpathStudy Kenya

Question 1

The ability of an organism to resist infections by the pathogens is called

Accepted Answer

Immunity — Immunity is the body's natural defense mechanism against pathogenic microorganisms, toxins, and other harmful substances. ---

Question 2

Name the group of pattern recognition molecules which functions exclusively as a signaling receptor

Accepted Answer

Toll-like receptor — Toll-like receptors (TLRs) are pattern recognition receptors that recognize PAMPs and function exclusively as signaling receptors. ---

Question 3

Name the first cells which are recruited at the place of infection

Accepted Answer

Neutrophils — Neutrophils are the first immune cells to arrive at the site of infection during acute inflammation. ---

Question 4

Which of the following antibody gives a primary immune reaction

Accepted Answer

IgM — IgM is the first antibody produced during a primary immune response and is most effective at complement activation. ---

Question 5

Which of these is NOT a characteristic feature of adaptive immunity

Accepted Answer

Antigen non-specific — Adaptive immunity is highly antigen-specific, unlike innate immunity which is non-specific. ---

Question 6

The major role of the complement system is to work in conjunction with

Accepted Answer

Antibodies to lyse cells via the C8 and C9 components — The complement system works with antibodies to form the membrane attack complex (MAC) using C5b-C9 components. ---

Question 7

One principal function of complement is to

Accepted Answer

Bind antibodies attached to cell surfaces and to lyse these cells — The complement system binds to antibodies on target cells and forms MAC to lyse the cells. ---

Question 8

Complement component C3 is cleaved by

Accepted Answer

C3bBb — C3bBb is the C3 convertase of the alternative pathway that cleaves C3 into C3a and C3b. ---

Question 9

The membrane attack complex in the complement pathway consists of

Accepted Answer

C5b,6,7,8,9 — The membrane attack complex (MAC) is formed by complement components C5b, C6, C7, C8, and C9. ---

Question 10

Acute inflammation can be initiated by

Accepted Answer

Mast cell activation — Mast cell activation releases inflammatory mediators like histamine, which initiate acute inflammation. ---

Question 11

Clonal selection occurs when antigen is encountered by

Accepted Answer

T-cell — Clonal selection is the process where specific T cells that recognize a particular antigen are selected for proliferation. ---

Question 12

Complement component C3b

Accepted Answer

Opsonizes bacteria — C3b is a major opsonin that coats bacteria, marking them for phagocytosis by immune cells. ---

Question 13

Naturally acquired active immunity would be most likely acquired through which of the following processes

Accepted Answer

Infection with disease-causing organism followed by recovery — Naturally acquired active immunity occurs when the immune system responds to a natural infection. ---

Question 14

Which of the following convey the longest-lasting immunity to an infectious agent

Accepted Answer

All of these — Naturally acquired active immunity provides the longest-lasting protection through memory cell development. ---

Question 15

Which of the following substances will not stimulate an immune response unless they are bound to a larger molecule

Accepted Answer

Hapten — Haptens are small molecules that become immunogenic only when conjugated to larger carrier molecules. ---

Question 16

B and T cells are produced by stem cells that are formed in

Accepted Answer

Bone marrow — Hematopoietic stem cells in the bone marrow give rise to all blood cells, including B and T cell precursors. ---

Question 17

B cells mature in the....... while T cells mature in the........

Accepted Answer

Bone marrow and GALT/Thymus — B cells mature in bone marrow and GALT, while T cells migrate to and mature in the thymus. ---

Question 18

Which of the following immune cells/molecules are most effective at destroying intracellular pathogens

Accepted Answer

T cytolytic cells — T cytolytic cells (CD8+ T cells) are specialized to kill cells infected with intracellular pathogens. ---

Question 19

A living microbe with reduced virulence that is used for vaccination is considered

Accepted Answer

Attenuated — Attenuated microorganisms are live pathogens that have been weakened to stimulate immunity without causing disease. ---

Question 20

B cells that produce and release large amounts of antibody are called

Accepted Answer

Plasma cells — Plasma cells are differentiated B cells specialized for antibody production. ---

Question 21

The specificity of an antibody is due to

Accepted Answer

The variable portion of the heavy and light chain — The variable regions of both heavy and light chains form the antigen-binding site, determining antibody specificity. ---

Question 22

In agglutination reactions, the antigen is a....... in precipitation reactions, the antigen is a......

Accepted Answer

whole cell/soluble molecule — Agglutination involves clumping of whole cells, while precipitation involves soluble antigens. ---

Question 23

B Cells are activated by

Accepted Answer

Antigen — B cells are activated when their surface immunoglobulin receptors bind to specific antigens. ---

Question 24

Fusion between a plasma cell and a tumor cell creates a

Accepted Answer

Hybridoma — Hybridomas are created by fusing plasma cells with tumor cells to produce monoclonal antibodies. ---

Question 25

Monoclonal antibodies recognize a single

Accepted Answer

Epitope — Monoclonal antibodies are produced by identical B cell clones and recognize a single specific epitope. ---

Question 26

Cell-mediated immunity is carried out by...... while humoral immunity is mainly carried out by......

Accepted Answer

T cells/B cells — Cell-mediated immunity involves T cells, while humoral immunity involves B cells producing antibodies. ---

Question 27

The ability of the immune system to recognize self-antigens versus non-self-antigen is an example of

Accepted Answer

Tolerance — Immune tolerance allows the immune system to distinguish between self and non-self antigens. ---

Question 28

Which of the following antibodies would most likely be found in body secretions such as tears, milk, saliva and mucus

Accepted Answer

IgA — IgA is the predominant antibody in mucosal secretions and provides protection at body surfaces. ---

Question 29

Which antibody is the first to be released into the blood following an infection

Accepted Answer

IgM — IgM is the first antibody produced during a primary immune response. ---

Question 30

Which is NOT true of memory cells

Accepted Answer

Are natural killer cells — Memory cells are long-lived B and T cells that provide rapid response upon re-exposure to antigen, not NK cells. ---

Question 31

An antigen that over stimulates the immune system by binding non-specifically to MHC on antigen presenting cells is termed a

Accepted Answer

Super antigen — Superantigens bind directly to MHC class II molecules, causing massive T cell activation. ---

Question 32

The variable regions in the light chains participate in

Accepted Answer

Epitope binding — Variable regions of light chains form part of the antigen-binding site for epitope recognition. ---

Question 33

Which of the following does not protect body surfaces

Accepted Answer

Salivary amylase — Salivary amylase digests starch but does not provide antimicrobial protection. ---

Question 34

Which of the following immunity is obtained during a lifetime

Accepted Answer

Both A and B — Both acquired and active immunity are obtained during a person's lifetime through exposure or vaccination. ---

Question 35

Which of the following statements is true about the IgM of humans

Accepted Answer

IgM is primarily restricted in the circulation — IgM is a large pentameric antibody primarily found in the bloodstream due to its size. ---

Question 36

Immunoglobulin classes are distinguished by the type of

Accepted Answer

heavy chains they possess — Different immunoglobulin classes are distinguished by their heavy chain constant regions. ---

Question 37

The variable regions in the light chains participate in

Accepted Answer

Epitope binding — Variable regions of light chains work with heavy chains to form the antigen-binding site. ---

Question 38

Which of the following immunity is obtained during a lifetime

Accepted Answer

Both A and B — Both acquired and active immunity develop during an individual's lifetime. ---

Question 39

Which of the following statements is true about the IgM of humans

Accepted Answer

IgM is primarily restricted in the circulation — Due to its large structure, IgM is mainly confined to the vascular system. ---

Question 40

Which of the following cells of the immune system do not perform phagocytosis

Accepted Answer

Basophil — Basophils are involved in allergic reactions through degranulation but do not perform phagocytosis. --- ## SECTION B: ESSAY QUESTION (10 MARKS) ### Question: Explain how APCs and MHC I and II collaborate to prevent spread of an infection (10 Marks) ### Answer: Antigen Presenting Cells (APCs) and Major Histocompatibility Complex (MHC) molecules work together in a sophisticated system to prevent the spread of infections through effective immune surveillance and response coordination. #### MHC Class I Pathway (Endogenous Antigen Presentation) MHC Class I molecules are present on all nucleated cells and present intracellular peptides to CD8+ T cells. When cells are infected by intracellular pathogens such as viruses, the pathogen's proteins are degraded by the proteasome in the cytoplasm. The resulting peptides are transported into the endoplasmic reticulum via TAP (Transporter associated with Antigen Processing) proteins, where they bind to newly synthesized MHC Class I molecules. This MHC I-peptide complex is then transported to the cell surface. CD8+ T cells (cytotoxic T lymphocytes) recognize these foreign peptides presented on MHC Class I molecules through their T cell receptors. Once activated, these cytotoxic T cells release perforin and granzymes, leading to the destruction of infected cells before the pathogen can replicate and spread to neighboring cells. #### MHC Class II Pathway (Exogenous Antigen Presentation) Professional APCs, including dendritic cells, macrophages, and B cells, express MHC Class II molecules and specialize in presenting exogenous antigens. These cells capture pathogens or pathogen-derived materials from the extracellular environment through phagocytosis, pinocytosis, or receptor-mediated endocytosis. The internalized antigens are processed in endosomal/lysosomal compartments where they are degraded by acidic proteases. MHC Class II molecules, synthesized in the endoplasmic reticulum and initially associated with the invariant chain, are transported to these compartments. The invariant chain is then cleaved, leaving CLIP (Class II-associated invariant chain peptide), which is subsequently replaced by the processed antigenic peptides through the action of HLA-DM. The MHC II-peptide complexes are then transported to the cell surface where they are recognized by CD4+ T helper cells. This recognition, along with co-stimulatory signals, leads to T helper cell activation and proliferation. #### Collaborative Prevention of Infection Spread The collaboration between APCs and MHC molecules prevents infection spread through several mechanisms: 1. Early Detection and Response: Dendritic cells act as sentinels in tissues, capturing antigens and migrating to lymph nodes where they present processed antigens to naive T cells, initiating adaptive immune responses before widespread infection occurs. 2. Coordinated Immune Activation: MHC Class II presentation by APCs activates CD4+ T helper cells, which then provide help to CD8+ T cells (through cytokine production) and B cells (for antibody production), creating a coordinated immune response. 3. Memory Formation: The presentation of antigens by APCs leads to the formation of memory T and B cells, providing long-term protection against reinfection. 4. Cross-Presentation: Some dendritic cells can present exogenous antigens on MHC Class I molecules (cross-presentation), allowing for CD8+ T cell responses against pathogens that don't directly infect the dendritic cells. 5. Immune Surveillance: The continuous presentation of self and foreign peptides on MHC molecules allows the immune system to monitor cellular health and detect abnormal or infected cells throughout the body. This integrated system ensures that infections are detected early, appropriate immune responses are mounted, and immunological memory is established to prevent future infections by the same pathogen.

Cellular I mmunology | MCQ Quiz | OmpathStudy Kenya

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