Question

1. what is the function of memory b cells?

a) kill infected cells
b) initiate the complement cascade
c) provide a rapid immune response during subsequent exposures
d) neutralize toxins directly

1. what happens in a positive result in the complement fixation test?

a) sheep red blood cells are lysed
b) no lysis of sheep red blood cells occurs
c) complement is degraded
d) a colored product is formed

1. which of the following diagnostic tests involves the use of fluorescent dyes?

a) elisa
b) agglutination test
c) precipitin ring test
d) fluorescent antibody test

Explanation:

• Question 5: Memory B cells are part of the adaptive immune system. Their key role is to "remember" a pathogen. When the body is re - exposed to the same pathogen, memory B cells quickly differentiate into plasma cells (which produce antibodies) or more memory B cells, leading to a rapid immune response.
• Option a: Killing infected cells is mainly the function of cytotoxic T cells (not memory B cells).
• Option b: Initiating the complement cascade can be done by antibodies (in the classical pathway) or other molecules (in alternative or lectin pathways), not a direct function of memory B cells.
• Option d: Neutralizing toxins directly is more of a function of antibodies (produced by plasma cells, which can be derived from memory B cells, but not the direct function of memory B cells themselves).
• Question 6: In the complement fixation test, if there is a positive result (i.e., the complement has been "fixed" by the antigen - antibody complex in the test system), there is no complement left to lyse the sheep red blood cells (which are added as an indicator).
• Option a: Sheep red blood cells are lysed in a negative complement fixation test (when complement is not fixed by the test antigen - antibody complex and can then act on the sheep red blood cells).
• Option c: Complement is not degraded in the sense described in the context of a positive test result; it is used up (fixed) in the antigen - antibody - complement interaction.
• Option d: A colored product formation is not a characteristic of the complement fixation test result readout.
• Question 7: The fluorescent antibody test uses fluorescent dyes. These dyes are conjugated to antibodies, and when the antibody binds to its target antigen (in a sample, such as on a slide), the fluorescence can be visualized under a fluorescence microscope.
• Option a: ELISA (Enzyme - Linked Immunosorbent Assay) uses enzymes (not fluorescent dyes) to produce a color change (usually via a substrate - enzyme reaction).
• Option b: Agglutination tests rely on the clumping (agglutination) of particles (like cells or latex beads) coated with antigens or antibodies, not fluorescent dyes.
• Option c: The precipitin ring test is based on the formation of a precipitation ring between antigen and antibody in a gel - like medium, not involving fluorescent dyes.

Answer:

1. c) Provide a rapid immune response during subsequent exposures
2. b) No lysis of sheep red blood cells occurs
3. d) Fluorescent antibody test