With this equation we can find a series of values of the variable, that correspond to each of a series of values of x, the independent variable. The parameters α and β have to be estimated from the data. The parameter signifies the distance above the baseline at which the regression line cuts the vertical (y) axis; that is, when y = 0. The parameter β (the regression coefficient ) signifies the amount by which change in x must be multiplied to give the corresponding average change in y, or the amount y changes for a unit increase in x. In this way it represents the degree to which the line slopes upwards or downwards.
The consequences of acute cellular rejection are variable. While it can predispose to glucocorticoid-resistant rejection and graft loss, most episodes do not have long-term adverse effects except in hepatitis C virus (HCV)-positive patients [ 7 ] (see 'Hepatitis C' below). Furthermore, acute cellular rejection identified by protocol liver biopsy in the absence of biochemical dysfunction often resolves without increasing immunosuppression [ 8 ]. There is even a suggestion that such subclinical immune activation might be beneficial in inducing a degree of tolerance [ 9 ]. The timing of rejection might affect outcomes. In a large retrospective study, early acute rejection was associated with better graft survival and late acute rejection was associated with reduced graft survival, when compared with graft survival rates in patients without an episode of rejection [ 4 ]. Patients who developed late acute cellular rejection had a 28 percent rate of chronic rejection and a 6 percent risk of graft failure.