The major immunoglobulin family to which a particular immunoglobulin belongs can be determined by sequential analysis of the 110 amino acids beginning from the

Correct Answer: C

Rationale: Heavy chain constant region (C-terminus, C) defines isotype; variable regions (A, B) or light chain don't.

Correct Answer: B

Rationale: B lymphocytes differentiate into plasma cells; T cells don't.

Correct Answer: A

Rationale: MHC class I molecules are self-identification molecules found on all nucleated host cells. Natural killer cells, after making contact with cells expressing stress signals, make the decision whether to kill them or not by assessing whether they express the appropriate types and levels of MHC I molecules. Although they are members of the innate immune system, natural killer cells do not recognize nonself, pathogen-associated molecular patterns, or pattern recognition receptors. Natural killer cells are unable to recognize somatically generated cell surface receptors.

Correct Answer: C

Rationale: IgG is the most abundant immunoglobulin in serum (~80%), key for systemic immunity.

Correct Answer: B

Rationale: Macrophages derive from monocytes and reside in tissues as phagocytic cells, not granulocytes.