What type of immune cells do macrophages interact with to activate the adaptive immune response?

Macrophages play a crucial role in bridging the innate and adaptive immune responses. They achieve this primarily through their interaction with T cells. When macrophages engulf pathogens, they process and present antigens derived from these pathogens on their surface using Major Histocompatibility Complex (MHC) molecules. The presentation of these foreign antigens is essential for the activation of T cells, particularly CD4+ (helper) and CD8+ (cytotoxic) T cells.

Upon recognizing the antigen-MHC complex on the macrophage, T cells become activated. This activation leads to a series of immune responses, including the proliferation of T cells and their differentiation into various effector functions such as cytokine production and the ability to kill infected cells. Additionally, activated T cells provide help to B cells, promoting antibody production, thus linking the cellular and humoral arms of the adaptive immune response.

While B cells, NK cells, and antigen-presenting cells (which include macrophages but are not the primary focus here) are all important components of the immune system, the specific interaction that is pivotal for initiating the adaptive response in this context involves macrophages and T cells directly.