Foreign-body response leukocytes

The extent and duration of tissue reactions to polymeric implant materials is important in assessing biocompatibility. In general, the ideal foreign body reaction in soft tissue to a pol nneric implant is one in which the acute inflammatory response, marked by pol3nnorpho-nuclear leukocytes, exudation and hyperemia, resolves quickly with little or no chronic inflammatory phase, marked by lymphocytes, plasma cells or histiocytes, and increasing fibrosis and eventual encapsulation of the implant by fibrous tissue occurs (7-9). Interaction of the tissue with the polymeric implant may result in a continuation of the chronic inflammatory phase or lead to increased fibrosis. This increased fibrosis or over-development of the fibrous capsule may involve adjacent organs or tissues and lead to adverse reactions (10, 11). 

Blood-contacting materials have to fulfill particular requirements, as they are immediately exposed to all host defense mechanisms of the body. Thus, the contact of blood with foreign surfaces induces several cascade reactions and activation phenomena. These complex and highly interconnected reactions potentially create clinically significant side effects in the application of medical devices (e.g., cardiovascular implants, extracorporeal circulation, catheters) and interfere with the success of the medical treatments [64]. In certain cases, even the formation of thromboemboli or systemic inflammatory reactions were reported to occur as a consequence of the activation of coagulation enzymes and thrombocytes and/or the activation of the complement system and leukocytes (immune response) at the biointerfaces of the applied materials [65]. 

Tissue type is determined hy molecules on the surface of every cell in the body. These molecules are called human leukocyte antigens (HLA) or the major histocompatibility complex (Petersdorfet et al. 1998 Villard 2006). Each person has unique HLAs. The HL As on the cells of the transplant signal to the body that this tissue is foreign, when a person receives a transplant, and stimulate an immune response. The recipient s blood usually is screened for antibodies against the tissues of the specific potential donor. If these antibodies are present severe rejection is expected, and transplantation will not be performed in these cases (Matas and Schnitzler 2004 Talbot and Manas 1997). 

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