Mechanisms whereby lytic granules from cytotoxic T lymphocytes damage guinea pig ventricular myocytes.
During immunological rejection of the transplanted heart, cytotoxic T lymphocytes (CTL) infiltrate the myocardium and by damaging the myocytes contribute to loss of function. To address one important aspect of heart transplant rejection, we investigated in guinea pig ventricular myocytes how CTL-derived lytic granules containing the pore-forming protein perforin reduce the membrane potential (VM) and cause cell damage. The reduction in VM was biphasic; within 8.4 +/- 1.9 min VM was reduced from a control value of -78.4 +/- 1.9 mV to -69.9 +/- 3.5 mV. Subsequently, within 6.7 +/- 2.1 min VM declined to -3.4 +/- 1.2 mV, associated with a progressive contracture. Under whole cell voltage clamp, in myocytes held at their resting potential (VM = -76.2 +/- 0.9 mV), granules induced discrete inward current steps (resembling 'single channel' activity), with a mean amplitude of -86.8 +/- 1.4 pA and open times lasting from seconds up to several minutes. The mean conductance and reversal potential calculated from the linear regression analysis of the I-V relations were 1390 pS and -6.8 mV, respectively. The probable non-selectivity of these 'channels' and the resultant loss of membrane K+ selectivity can account for the reduction in VM. At the same time, opening of these pores leads to Ca2+ overload, resulting in contracture and cell damage.
Binah
O
O
Department of Pharmacology, College of Physicians and Surgeons of Columbia University, New York.
Kline
R
R
Berke
G
G
Hoffman
B
B
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D003594:Cytoplasmic Granules / Q000276:immunology*; D006084:Graft Rejection; D006168:Guinea Pigs; D006352:Heart Ventricles; D007473:Ion Channels / Q000502:physiology; D008564:Membrane Potentials; D009206:Myocardium / Q000276:immunology*; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*
D007473:Ion Channels; D002118:Calcium