Release of Immune Modulation Factors from Platelet Concentrates during Storage after Photochemical Pathogen Inactivation.

Background. Platelets (plt) prepared for transfusion contain multiple molecules that modulate immune function, mediate acute transfusion reactions, induce immune responses, and affect hemostasis. These cytokines/chemokines are secreted differentially from plt during storage (

Aims. The INTERCEPT Blood System (IBS) for platelets utilizes amotosalen-HCl (S-59) with ultraviolet A (UVA) light to inactivate a broad spectrum of pathogens and leukocytes. This study was designed to evaluate the effects of photochemical treatment on in vitro release of immune modulation molecules after processing during 7 days (d) of storage.

Methods. Platelet concentrates (n = 10) collected by aphaeresis (CPA) with process leuko-reduction (< 10⁶) containing 8.15x10¹¹ ± 0.8 platelets were suspended in 35% donor plasma and 65% platelet additive solution (Intersol, Baxter, France) and divided into two equal components. One served as an untreated control (C) and the other was prepared with 150 uM amotosalen and a 3 J/cm² UVA photochemical treatment (PCT) and stored at 22°C with shaking for 7 days. Platelet concentration (10⁶/uL), pH and levels of immune modulation factors were measured: CD62p(ng/mL), PDGF-AB(ng/mL), IL8(pg/mL), sCD40L(pg/mL), IL1β(pg/mL) and TNFα(pg/mL). The concentration of each factor was determined by specific enzyme linked immunosorbent assays in plt and supernatant (s) fractions isolated from stored PCT and C plt components. Mean values ± SD were calculated and compared by paired t-test.

Results. Platelet content, pH and cytokine/chemokine content and release from CPA prepared with photochemical treatment were not statistically different (p > 0.05) from C during 7 d of storage (Table). From d1 to d7, the pH of PCT and C units decreased similarly, but remained within acceptable ranges. No detectable IL1β and TNFα were observed in PCT or C CPA. During platelet storage CD62p, PDGF-AB, IL8, and sCD40L increased similarly in supernatants of PCT and C units. The increase in supernatant levels correlated with a decrease of these cytokines in plt. Platelets in PCT and C retained measurable levels of CD62, IL8, sCD40L and PDGF-AB though 7 d. Levels of sCD40L demonstrated marked variation.

Conclusions. Cytokines increased moderately in the supernatants of CPA and decreased in platelets during storage. After 7 d C and PCT platelets in CPA retained detectable levels of cytokines. PCT had no differential influence on release of immune modulation molecules in vitro over 7 d of storage.