beta-Lysin of platelet origin.

(3-Lysin is the name that Pettersson proposed to distinguish this thermostabile bactericidal component of serum from Buchner's alexin or a-lysin (51). He defined (8-lysin as the bactericidal substance found in normal serum that resisted inactivation when heated to 56°C for 30 min. According to this definition, there are at least three different ,3-lysins found in normal serum; these consist of lysozyme, ,B-lysin from platelets, and (8-lysin of nonplatelet origin. The first of these, lysozyme, is a single entity which is well defined in regard to its chemical and biological properties. The other two types of (3lysins are not readily distinguished from each other, and each could be composed of several distinct molecules. The ,B-lysin of platelet origin may be similar or identical to plakin (23). The (8-lysin of nonplatelet origin may include the bactericidal cationic proteins isolated from leukocyte lysosomes (64-66). In this review, attention will be focused on the (3-lysin of platelet origin, which will be referred to as "platelet (3lysin."