Which cells are incapable of secreting immunoglobulins?

T lymphocytes are indeed the cells that are incapable of secreting immunoglobulins. The primary role of T lymphocytes is to participate in cell-mediated immune responses rather than humoral immunity. Unlike B lymphocytes, which can differentiate into plasma cells that produce and secrete antibodies (immunoglobulins), T lymphocytes help regulate immune responses and kill infected cells directly.

Plasma cells, which are differentiated B lymphocytes, are specifically designed for the production and secretion of immunoglobulins, making them a crucial component of the adaptive immune response. Follicular dendritic cells are important for presenting antigens to B lymphocytes and aiding in the activation of these cells, but they do not produce immunoglobulins either.

Understanding the functions of different immune cells helps clarify the diverse roles they play in the immune system, highlighting why T lymphocytes do not produce immunoglobulins while others do.