Final answer:
Cytokines are essential for initiating the immune response and are involved in a plethora of activities, from mediating inflammation to cell signaling. They are released by various immune cells and can act both locally and systemically. The statement about cytokines' involvement in initiating the immune response is true.
Step-by-step explanation:
The statement 'Cytokines involved in initiating the immune response' is true. Cytokines are glycoproteins secreted by a diverse range of cells such as leukocytes, macrophages, and fibroblasts. They play a crucial role in the immune response, particularly by mediating inflammation and invoking the production of inflammation-eliciting mediators like acute-phase proteins, histamine, leukotrienes, prostaglandins, and bradykinin. Furthermore, cytokines are involved in cell signaling within the immune system, facilitating the communication between cells. They can act both locally and systemically as autocrine or paracrine factors, enhancing cellular defenses by stimulating the proliferation of progenitor cells and boosting general disease resistance.
There are various subtypes of cytokines, such as colony-stimulating factors and interleukins, which play significant roles in immune system regulation. Interleukins, for example, are pivotal in mediating interactions between leukocytes and bridging the innate and adaptive immune systems. Cytokines can establish a positive feedback loop upon pathogen recognition, which leads to a cytokine burst, intensifying the immune response. Helper T cells and cytotoxic T cells, both subtypes of T cells, also utilize cytokines. Helper T cells, which release cytokines, and cytotoxic T cells, which kill infected cells, are distinguished by their respective surface markers CD4+ and CD8+.