Which represents an autocrine effect of IL-2?

Which represents an autocrine effect of IL-2?

• A. Increased IL-2 receptor expression by the Th cell producing it
• B. Macrophages signaled to the area of antigen stimulation
• C. Proliferation of antigen-stimulated B cells
• D. Increased synthesis of acute-phase proteins throughout the body

Answer: (A)

Autocrine signaling is when a cell responds to a signal it itself releases by upregulating its own receptors. Here, a helper T cell that has secreted IL-2 also increases its IL-2 receptor (CD25) on its surface, so the IL-2 it makes can act back on that same cell to drive its own proliferation. This self-stimulation is the defining autocrine effect. By contrast, signaling that affects nearby cells (paracrine) or distant sites (endocrine) isn’t autocrine. For example, signals that recruit macrophages to the infection site, or stimulate B-cell proliferation or liver production of acute-phase proteins, involve other cells or broader systemic responses rather than the producing cell acting on itself.

Autocrine signaling is when a cell responds to a signal it itself releases by upregulating its own receptors. Here, a helper T cell that has secreted IL-2 also increases its IL-2 receptor (CD25) on its surface, so the IL-2 it makes can act back on that same cell to drive its own proliferation. This self-stimulation is the defining autocrine effect.

By contrast, signaling that affects nearby cells (paracrine) or distant sites (endocrine) isn’t autocrine. For example, signals that recruit macrophages to the infection site, or stimulate B-cell proliferation or liver production of acute-phase proteins, involve other cells or broader systemic responses rather than the producing cell acting on itself.