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. 2024 Jan 26;25(3):1553. doi: 10.3390/ijms25031553

Figure 2.

Figure 2

Schematic representation of the innate and adaptative immune systems. The innate immune system encompasses neutrophils, eosinophils, antigen-presenting cells (APCs), such as macrophages and dendritic cells (DCs), and natural killer (NK) cells. Activation of the innate immune system is achievable through the recognition of soluble pathogen-associated molecular pattern molecules (PAMPs) by pattern recognition receptors (PRRs), such as toll-like receptors (TLRs), on innate immune cells. TLR-ligand binding induces downstream signaling pathway activation, which ultimately leads to the production of proinflammatory cytokines. APCs constitute the bridge between the innate and adaptive immune systems. APCs activate T cells through the binding of CD40 with the CD40 ligand, major histocompatibility class (MHC) II binding with the T cell receptor, and cytokine-specific receptor stimulation. T cell differentiation is ultimately regulated by the nature of the given cytokine. The figure was partly generated using Servier Medical Art provided by Servier and licensed under a Creative Commons Attribution 3.0 Unported license.