The primary mechanism of immunosuppressive drugs involves the suppression of various components of the immune system. Drugs such as Cyclosporine, Tacrolimus, and Azathioprine target specific lymphocytes, reducing their activity and proliferation. Corticosteroids work by inhibiting the production of inflammatory cytokines, while other agents like Mycophenolate mofetil inhibit nucleotide synthesis, affecting lymphocyte function.