A 4-year-old-girl sees her physician because of a severe necrotizing,oropharyngeal herpes simplex viral (HSV)infection.She has a past medical history of cytomegalovirus (CMV)pneumonitis and cutaneous HSV infection.Phenotypic analysis of her blood cells shows an absence of CD56⁺ and CD16⁺ cells.There are normal numbers of CD4⁺ and CD8⁺ cells in the blood,and serum antibody titers are normal.The patient's CD8⁺ T cells were able to kill virally infected target cells in vitro.Which of the following is NOT characteristic of this girl's immunodeficiency disease?

Question

Quizplus · Accepted Answer

The presence of normal numbers of CD8⁺ T cells and the ability of these cells to kill virally infected target cells indicates that the class I major histocompatibility complex (MHC)pathway of viral peptide antigen presentation is intact.The patient's immunodeficiency is due to a lack of natural killer (NK)cells.NK cells express CD56 and/or CD16.NK cells are activated by interleukin-15 (IL-15)and IL-12,are normally inhibited by recognizing class I MHC on other cells,kill target cells with altered class I MHC expression through a granzyme B-dependent mechanisms (similar to cytolytic T lymphocyte killing),and produce interferon-$\gamma$ as part of the early innate response to viral infection.

A 4-Year-Old-Girl Sees Her Physician Because of a Severe Necrotizing,oropharyngeal γ\gammaγ

A 4-Year-Old-Girl Sees Her Physician Because of a Severe Necrotizing,oropharyngeal $\gamma$