Polymorphonuclear leukocytes in coagulating whole blood recognize hydrophilic and hydrophobic titanium surfaces by different adhesion receptors and show different patterns of receptor expression.

The mechanism of healing or rejection of implant materials is unknown, but the process always starts at the contact with coagulating blood. Here, the initial reactions of clean (hydrophilic) and alkylated (hydrophobic) titanium with blood were investigated by short-term exposure to human blood and detection of polymorphonuclear leukocyte (PMNL) surface antigens with an immunofluorescence technique. The fluorescence intensity was quantitated by computer-aided image analysis. Antibodies specific to CD11b, CD16, CD18, CD62L, and CD162 were used to block PMNL adhesion. The respiratory burst of adhering cells was stimulated with opsonized zymosan and measured by chemiluminiscence. The thrombin dependence of PMNL reactions was studied by using hirudin, a specific thrombin inhibitor. The expression of CD62L decreased with increasing exposure time, and the rate of decrease was faster at the hydrophilic surface. At the hydrophilic surface, the CD16 exposure was high after 8 minutes of blood contact, and it decreased with time. At the hydrophobic surface, a peak in CD16 expression was seen after 32 minutes of blood exposure. At the hydrophobic surface, the expression of CD11b increased slowly with increasing blood exposure time, whereas at the hydrophilic surface, a peak of CD11b expression was seen after 32 minutes of blood exposure. The expression of CD11b and that of CD16 were found to be thrombin dependent. At the hydrophilic surface, adhesion of PMNLs was blocked by CD16 antibodies, whereas adhesion to the hydrophobic surface was blocked by anti-CD162. Mixing blood with antibodies to CD11b, CD18, and CD62L amplified the adhesion of PMNLs to the hydrophilic surface.