From where did you get the lymphocytes? peripheral blood?
Lymphocytes in peripheral blood are differentiated cells, and can not proliferate anymore, except young lymphocytes in blood from leukemic patients that contains lymphoblast. To culture lymphocyte, you need to add phytohemeagglutinin (PHA) as a mitogen, and culture in suspension method, because lymphocytes do not adhere to plastics such as mesenchymal stem cells, or other adherent cells. This kind of culture is usually done to make chomosomal specimens to get the karyotype of a patient.
I am not sure, as I never tried to let them adhere to the flask. If they just adhere, may be yes, but surely not proliferate. I used to add PHA to force them back into limphoblast, and proliferate, and harvest after 72 hours, without changing medium.