Question

a specific immune response begins when a white blood cell comes in contact with an antigen (any substance that the immune system does not recognize as part of the body). what external factor typically triggers a specific immune response?
a. a fluctuation of the external air pressure
b. a large release of adrenalin by the endocrine system
c. a change in the external temperature
d. an invasion of a microorganism from the external environment

Explanation:

特异性免疫反应通常由外界环境中的微生物入侵引发，微生物可作为抗原刺激白细胞引发免疫反应。A选项外界气压波动、B选项内分泌系统大量释放肾上腺素、C选项外界温度变化一般不直接触发特异性免疫反应。

Answer:

D. an invasion of a microorganism from the external environment