Inhibition of activation of human T lymphocytes by the complement C1 esterase inhibitor

• Published in: Immunology 1995-10, Vol.86 (2), p.304-310
• Main Authors: Eriksson, H, Sjögren, H O
• Format: Article
• Language: English
• Subjects: Complement C1 - immunology; Complement C1 Inactivator Proteins - pharmacology; Electrophoresis, Polyacrylamide Gel; Enterotoxins - immunology; Humans; Interleukin-2 - immunology; Lymphocyte Activation - drug effects; Lymphocyte Activation - immunology; Staphylococcus aureus - immunology; T-Lymphocytes - immunology
• ISSN: 0019-2805; 1365-2567

The major histocompatibility complex (MHC) class I molecules have been shown to be substrates to both of the complement C1 esterases. The effect of a C1 esterase-mediated cleavage of the MHC class I molecules on the activation process of lymphocytes was investigated by including the complement C1 esterase inhibitor (C1-Inh) in the medium during activation of human peripheral lymphocytes by staphylococcal enterotoxin A (SEA). The C1-Inh was shown to inhibit the activation of both CD4+ and CD8+ cells. No effect on activation of B lymphocytes was recorded, although the complement C1 complex was shown to bind to the B lymphocytes. Furthermore, the C1 complex bound to mononuclear cells was shown to be cleaved into molecular weights corresponding to the activated forms of the C1 esterases. The effect of the C1-Inh was much more pronounced at low cell density and the inhibition was not affected by the addition of interleukin-2 (IL-2). However, the inhibition was reduced when the cells were disturbed by addition of new portions of C1-Inh, 24 and 48 hr after the initiation of the activation. This indicates that the C1-Inh interference with the activation of T lymphocytes is mediated through a mechanism that requires some form of cell contact.