Question

from where are b-lymphocytes and t-lymphocytes secreted?

Answer 1

Both of these cells are type of lymphocytes.
T- Lymphocyte originate in the bone marrow and mature in the thymus and destroy antigens directly by phagocytosis or by stimulating B -lymphocytes to secrete antibodies.

B lymphocytes also born and mature in bone marrow and produce antibodies or immunoglobulins.