Study of the kinetic and structural properties of a monoclonal immunoglobulin G cryoglobulin

The precipitation of a monoclonal IgG2 crystalline cryoglobulin (WEB) is shown to occur via a nucleation mechanism. The kinetics of precipitation fits the empirical equation 1n(t2/t1) = nù(c1/c2), where t is the time to reach half-maximum turbidity for concentration c. The effect of mild reduction of interchain disulfides on the kinetics and extent of precipitation have also been determined. Cleavage of only one or two inter heavy-heavy chain disulfide bonds appears to abolish cryoprecipitation. The extent of reduction at high reductant levels suggests that there is an extra inter heavy-heavy chain disulfide in IgG-WEB. Laser Raman spectroscopy detects no structural change between reduced (noncryoprecipitable) and native (cryoprecipitable) WEB, suggesting that perturbation of a local site is responsible for loss of cryoprecipitation.