Schematic model for the molecular basis of age-dependent T cell activation.

Abstract

Engagement of T cell receptors (TCR) and costimulatory CD28 receptors (blue) by soluble anti-CD3 Ab and/or anti-CD28 Ab stimulation promotes signaling cascades of adaptor proteins (LAT) and kinases (ERK). These trigger signal transduction pathways resulting in the activation of the transcription factors NFATc (red), NF-κB (white) and the association of AP-1 with cFos/cJun (green). These transcription factors cooperate with each other during the activation of the IL-2 promoter. Shown are the schematic molecular responses of (A) CB and (B) adult with soluble anti-CD3 Ab stimulation alone or together with costimulation by anti-CD28 Ab (blue) for (C) CB and (D) adult. A hypothetical molecular mechanism for infants aged 1–2 months (E) or 3–5 months (F) after TCR/CD3 engagement plus CD28 costimulation with unknown pErk response.</p