Final answer:
Immunoglobulins are not antibodies secreted by platelets. Antibodies, also known as immunoglobulins, are proteins produced and secreted by plasma cells for the humoral immune response.
Step-by-step explanation:
No, immunoglobulins are not antibodies secreted by platelets. Immunoglobulins, also known as antibodies, are proteins that are produced and secreted by plasma cells, which are differentiated B lymphocytes.
These antibodies play a crucial role in the humoral immune response. They bind antigens via variable domains and can neutralize pathogens, mark them for phagocytosis, or activate the complement cascade. There are five classes of antibodies - IgG, IgM, IgA, IgD, and IgE, each with its own functions and production sites.