PATHOLOGY

Detailed explanation-1: -In secondary antibody responses, memory B cells themselves can act as antigen-presenting cells and activate helper T cells, as well as being the subsequent targets of the effector helper T cells.

Detailed explanation-2: -Helper T cells become activated through a multistep process, which begins with antigen-presenting cells, such as macrophages. These cells ingest an infectious agent or foreign particle, partially degrade it, and export fragments of it-i.e., antigens-to the cell surface.

Detailed explanation-3: -Macrophages interact with T cells in order to bring about T cell activation in target organs, and are themselves activated by inflammatory messenger molecules (cytokines) produced by the T cells.

Detailed explanation-4: -Another quality of macrophages is their ability to present exogenous antigens on major histocompatibility complex (MHC) class I molecules in order to activate CD8+ T cells.