IUBio

What is the prime (') in F(ab)'2

Steven Shivers, Ph.D. SHIVERS at AARLO.MOFFITT.USF.EDU
Wed Sep 20 10:06:40 EST 1995


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



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