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A human multiple myeloma produced antibody which bound to sheep red blood cells. When guinea pig
Complement was added to the antibody-coated cells, they lysed. What did this result say about the
isotype (= Class) of the myeloma antibody?
A. The isotype was either IgA or IgM.
B. The isotype was either IgM or IgG.*
C. The isotype was either IgG or IgE.
D. The isotype was either IgE or IgD.
E. The isotype was either IgD or IgA.

Natural antibodies to ABO antigens are usually of IgM isotype, do not cross the placenta, and do not
cause problems if the fetus expresses a paternal ABO antigen lacking in the mother. However, ABO
antigens sometimes give rise to an IgG response. In which situation would there be the highest
probability of production of anti-ABO IgG that could produce erythroblastosis fetalis?
Mother’s Blood Type Father’s Blood Type
B. O AB*
C. A A
D. O O
E. O O Bombay

Allergen on the skin of an allergic person produced a ‘wheal-and-flare’ reaction, in which mast cells
released “inflammatory mediators” from their granules. How did these produce the flare?
A. Caused edema.
B. Increased responsiveness of sensory nerve endings.
C. Dilated small blood vessels.*
D. Induced local cell proliferation.
E. Stimulated migration of neutrophils to the area.
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