The relationship between free and total hydroxyproline concentration in blood serum and urinary excretion of hydroxyproline in healthy individuals

The quantitative measurement of the IgG subclass composition of the sera from sixteen patients with cystic fibrosis has revealed grossly elevated levels of IgG4 in seven patients. The possible significance of this observation is discussed in relation to recent reports of a high incidence of immediate-type hypersensitivity in such patients.