After 2 years of hard work,a graduate student finally succeeds in creating a gene knockout mouse lacking CD4.The student is particularly careful to keep this mouse line in a microbe-free animal facility because these mice are expected to show:
A)No ability to produce IgM antibodies
B)Impaired ability to produce antibodies and activate macrophages
C)No ability to activate naive class I-restricted T cells
D)Complete absence of cytotoxic T lymphocyte (CTL)responses to viral infections
E)Failure to produce neutrophils

Question

Quizplus · Accepted Answer

Knockout mice lacking CD4 do not contain mature class II-restricted T cells because the CD4 coreceptor plays an essential role in the maturation of T cells in the thymus.Most CD4⁺ class II-restricted T cells are cytokine-producing helper cells that function in host defense against intracellular microbes.These helper T cells are critical for activating B cells to produce antibodies,and for activating macrophages to efficiently kill phagocytosed microbes.Knockout mice lacking CD4 therefore do not have any helper T cells.IgM antibody production is generally not dependent on help from CD4F1F1F1S1^F1F1F10 T cells.Because CD8 is still expressed,naive class I-restricted T cells are still present and able to respond to intracellular infections,although this ability may be impaired by lack of T cell help.Neutrophil production by the bone marrow should be relatively normal.

After 2 Years of Hard Work,a Graduate Student Finally Succeeds