On-pump coronary artery bypass grafting (CABG) triggers inflammatory responses as a result of surgical stress and extracorporeal circulation, which affect platelet and leukocyte activation while enhancing their intimate crosstalk. Given this, the study presented here aimed to investigate platelet-T cell interaction after CABG focusing on the changes in immunomodulatory subtypes of regulatory T Cells.

Blood samples were obtained from twenty patients undergoing on-pump CABG at 5 different time points of 24 h before, immediately, 2 h, 24 h, and one week after surgery. Total leukocyte and lymphocyte counts were determined using an automatic cell counter. Platelet P-selectin expression, frequencies of CD4⁺ and CD8⁺ T cells, platelet-T cell aggregates (PTCAs), and regulatory T cells derived from CD4⁺ (T4reg) and CD8⁺ (T8reg) cells, were assessed by flow cytometry.

A significant increase in total leukocyte count occurred immediately after CABG, whereas, conversely, lymphocyte and CD4⁺ T cells but not CD8⁺ T cells decreased 2 h after surgery. However, all these changes returned to pre-CABG baseline levels within a week. Platelet P-selectin expression increased immediately after surgery, followed by a two-hour delay after PTCA, and both returned to baseline after one week. T4regs and T8regs showed a similar increase and decrease trend, where T8regs but not T4regs returned to baseline one week after surgery.

CABG surgery induces an inflammatory response that activates platelets and enhances P-selectin expression, facilitating PTCA formation. This mechanism is critical for the dynamics and differentiation of T cells, which play an essential role in post-CABG modulation of immune responses.