Interleukin secreted by macrophages, stimulating lymphocytes is:
Macrophages release IL-1 which stimulates the T-helper cells.
The T-cells in response proliferate and release IL-2 which in turn stimulates still further T-cell proliferation and B cell proliferation and differentiation into plasma cells.

Thus

Macrophages release→IL-1*
T-helper cells release→ IL-2*
IL-1
INF alpha
TNF alpha
IL-6