Final answer:
CD4 helper T2 (Th2) lymphocytes are the T-lymphocyte phenotype central to the development of childhood asthma, through stimulation of IgE production and inflammatory responses.
Step-by-step explanation:
The T-lymphocyte phenotype that is the key determinant of childhood asthma is B) CD4 helper T2 (Th2) lymphocytes. These Th2 cells play a critical role in the immune response associated with asthma by stimulating naive B cells to secrete antibodies, particularly Immunoglobulin E (IgE), which is involved in allergic responses.
Moreover, Th2 cells release cytokines such as IL-4 and IL-13 that contribute to the recruitment and activation of eosinophils, leading to the inflammation characteristic of asthma.