AUTOANTIBODIES AGAINST MOUSE BROMELAIN-MODIFIED RBC ARE SPECIFICALLY INHIBITED BY A COMMON MEMBRANE PHOSPHOLIPID, PHOSPHATIDYLCHOLINE

  • 1 January 1985
    • journal article
    • research article
    • Vol. 55  (2) , 263-269
Abstract
Sera from mice injected 4 days earlier with lipopolysaccharide lysed mouse RBC (red blood cells) treated with bromelain (brom). This lytic activity was totally inhibited by including phosphatidylcholine at final concentrations of 2 .mu.g/ml, or more, in the lytic mixtures. The lytic activity of antibodies against rat RBC was not inhibited, even at concentrations of phosphatidylcholine up to 2.5 mg/ml. Various components of the phosphatidylcholine molecule, and other lipids including the closely-related molecule dipalmitoyl phosphatidyl-dimethylethanolamine which is identical to dipalmitoyl phosphatidylcholine except for the absence of a CH2 group on the polar head group, did not inhibit lysis by the autoantibodies. Autoantibodies against mouse brom RBC, but not antibodies against rat RBC, bound to, and could be eluted from, phosphatidylcholine molecules attached to an insoluble matrix. Liposomes of phosphatidylcholine prepared in the presence of phosphatidic acid or phosphatidylinositol did not inhibit the lysis of mouse brom RBC by autoantibodies to the same extent as liposomes of only phosphatidylcholine. This suggests that phosphatidylcholine is recognized by the autoantibodies only if presented in a certain configuration. Thus, the function of these autoantibodies may be to facilitate the removal of membrane-damaged cells from the body. Such cells may arise by the process of aging, or because of the effects of infectious agents such as viruses.