<prompt> Interleukin secreted by macrophages, stimulating lymphocytes isIFN alphaTNF alphaIL-1IL-6  <response>: IL1 IL6Macrophages release IL 1 which stimulates the T helper cells.The T cells in response proliferate and release IL 2 which in turn further stimulates T cell proliferation and B cell proliferation and differentiation into plasma cells.Please note that even IL-6 produced by macrophages acts on late stages of B cell differentiation enhancing antibody formation. Still, IL-1 being the most important cytokine having systemic effects of inflammation has been chosen as the answer here in preference to IL-6. 