Final answer:
The assertion that an antigen can only activate the immune system if it binds strongly to its immune cell receptor is false. The immune response can be triggered by multiple factors and involves interactions between B and T cells and the presentation of antigens.
Step-by-step explanation:
Whether an antigen needs to bind strongly to its immune cell receptor to activate the immune system is false. While strong binding can indeed activate the immune response, the immune system can also be activated by antigens that do not bind as strongly, as multiple interactions and signaling events can lead to activation.
This activation process is complex and involves the recognition of antigens by specific receptors on the surface of B and T cells. An antibody-antigen complex can trigger various responses such as phagocytosis, activation of the complement system, and agglutination. B cells, for example, require two signals for full activation: one from the native antigen binding to surface immunoglobulin and another from T cell-produced cytokines. Therefore, the strength of the antigen-receptor binding is important but not the sole determinant of immune activation.
The recognition of antigens by the immune system resembles a lock and key mechanism. The response to T cell-dependent antigens is a coordinated effort where B and T cells must come into close contact. This contact allows for antigen processing by B cells and subsequent interaction with T cells, leading to the full activation of B cells, which then act as antigen-presenting cells.