Attenuation of platelet-neutbophil interactions in sepsis with combinations of blocking antibodies

Introduction: Platelet-neutrophil (P-PMN) interactions contribute to impaired microvascular blood flow in severe sepsis (S). P-PMN adhesion can be attenuated by blocking cell receptors on either the P or the PMN. We examined whether blocking combinations of adhesive molecules further attenuates S induced P-PMN interactions. Methods: P's, PMN's, and normal platelet poor plasma (NPPP) were isolated from 12 normal subjects. Platelet poor plasma was isolated from 12 patients with S (SPPP). Combinations of blocking monoclonal antibodies (mAb) were added to desired cell Unes after incubation with SPPP and before coincubation of PMN and P. The following mAb's were used: anti-CD41 and abciximab block the P complex GPIIb-IIIa; anti-CD62P blocks P-selectin on P; anti-CD11a/LFA, anti-CD11b block receptors on PMN. Cell suspensions were infused at 1 ml/m through 5 u pore filters and the maximal point of the pressure time curve, Pi (mm Hg), was recorded. P-PMN interactions were assessed using fluorecscein conjugated mAb to activated CD63 P receptors. The mean intensity of mAb fluorescence (MF) of the PMN group was used as an index of P-PMN adhesion. Data are expressed as mean ± SE, *p<0.05 vs P+PMN+NPPP. Conclusions: In S, P-PMN interactions increase resistance to cell filtration. The addition of mAb's to multiple cell receptors leads to greater decreases in resistance to filtration by decreasing P-PMN aggregates than when mAb to single receptors are used alone. Results: Pi (mm Hg) MF(lfu) P+PMN+NPPP 19.0±1.0 317.8±47.4 P+PMN+SPPP 29.0±2.9* 730.4+135.3* P+CD41+CD62P+PMM+SPPP 22.7±2.5 387.4±75.1 P+CD41+PMN+D11b+SPPP 22.7±1.1 462.0+182.3 P+PMN+CD11b+CD11a/LFA+SPPP 19.0±3.6 393.8±99.4 P+CD41+Abciximab+PMN+SPPP 22.2±4.0 439.1±120.3.