The Origin of TH2 Responses

Helper T lymphocytes (TH cells) have multiple functions during human immune responses, including stimulating B cells, the "help" needed to spur antibody production. Naïve TH precursor cells give rise to four functionally distinct subsets that can be further divided into subtypes or regulated states. Once the first two TH subsets were recognized--TH1 and TH2 cells ()--the obvious question became: How does the immune system decide which response to make? Recent reports present an important advance in understanding the origins of TH2 responses and mechanisms of immune recognition of two medically important classes of antigens: helminth parasites and allergens.