Table 2.

Expression Patterns and Roles of JAK Family Members in Different Immune Cell Types

Immune Cell Type	JAK Expression	Role and Function	References
T cells	JAK1, JAK3 (lesser extent: JAK2, TYK2)	Crucial for T cell receptor (TCR) signaling and development	[88, 89]
		Initiate the activation of key transcription factors (STAT) essential for the differentiation of Th1 (STAT1/4), Th2 (STAT5/6), Th17 (STAT3/5), and Treg (STAT3/5) cell subsets	[17, 90]
B cells	JAK1, JAK3	Relay signals from the B-cell receptor (BCR) and cytokine receptors. JAK1 aids B cell development, JAK3 vital for maturation	[90, 91]
NK cells	JAK1, JAK3 (also: JAK2, TYK2 for NK development)	Transduce signals from cytokine receptors (IL-2, IL-15). Promote NK cell development, survival, and cytotoxicity	[92–95]
Neutrophils	JAK expression less explored	Implicated in cytokine release via JAK-STAT signaling. Influence pro-inflammatory responses	[94–97]
Monocytes	JAK1, JAK2	Essential for cytokine and growth factor signaling. Regulate monocyte activation, differentiation, and immune responses	[98–100]
Inflammatory macrophages	JAK1-3, TYK2	Initiate essential transcription factors (STAT and NF-κB) to trigger the differentiation process: M1 (STAT1, NF-κB), M2a (STAT3/6), M2b (NF-κB), and M-reg (STAT3)	[17, 90]
Dendritic cells (DC)	JAK1, JAK2, JAK3	Drive DC maturation, antigen presentation, and cytokine production	[101, 102]