I came across this question:
During the experiment compares immune response of lymphocytes of 2mo. young animal, to 2y old one.Noticed decrease response to Chlamidia in the older animal.
Age related change in which of the following cell types is the cause of decrease response.

1.B lymphocytes
2.Macrophages
3.Neutrofils
4.Plasma cells
5.T lymophocytes

I couldn't find the answer. Does anybody know to help me with this??
THank you
Dusha

Answer- T lymphocytes.
The question is about thymic involution. As the animal grows, the thymus involutes/atrophies---> decreased maturation of T-cells---> decreased response to infection relative to the younger animal.

OMG it was so obvious, I was not thinking clearly!! Thank you.
I have to readjust my thinking otherwise I will not pass the test!!
Thank you so much.
Dusha