In article <43ml4m$nma at netnews.upenn.edu>, David Peritt
<Peritt_d at a1.mscf.upenn.edu> wrote:
> I TA an undergrad Immunology and the proffessor was stumped by the
> history behind the prime in the nomenclature for f(ab)'2 and Fab'. Can
> anyone shed light on this??
>>Fab fragments containing the heavy chain hinge are called Fab'. If the
>>interchain disulfide bonds are intact, the two Fab' fragments remain
>>associated and are called F(ab')2.
>>M_rten Schneider, Dept. of Medical Immunology and Microbiology, Uppsala, Sweden.
>>(Marten.Schneider at immun.uu.se)
The above answer is almost right, but it doesn't go far enough. The
enzyme papain cleaves the Ig molecule above the interchain (H-H)
disulfide bonds, such that 2 Fab fragments are produced. The enzyme
pepsin cleaves the Ig molecule below the disulfide bonds so that the
2 fragments remain attached. Since the latter fragments are slightly
larger than the former ones, the fragments are represented as
F(ab)'2. Further cleavage of the disulfide bonds creates 2 Fab'
fragments, which are again slightly larger than the Fab fragments
produced by papain cleavage.
*****************************************
Steven C. Shivers, PhD
Bone Marrow Transplant Program
H. Lee Moffitt Cancer Center
at the University of South Florida
12902 Magnolia Dr.
Tampa, FL 33612