An oil activated fuel injector which provides a pilot quantity of fuel prior to the main fuel injection event. A pre-ignition threshold and a pre-ignition mitigating action are adjusted based on a rate of change of cylinder aircharge. A door is connected to the body and moves between an open position allowing access to the recess from outside the body and a closed position covering the opening. Since the transistor is not always on in a non-selection period, a shift of the threshold voltage of the transistor is suppressed. The receptor, together with peptides encoding its extracellular domain, have application in methods of immunomodulation, including the blocking or inhibition of humoral immune responses in transplant patients.