Conjugation of Hamster IgG

Richard R. Hardy rr_hardy at
Wed Sep 11 13:14:31 EST 1996

In article <5141dn$5er at>, Paula Lavery
<plaver at PO-Box.McGill.CA> wrote:

>Hi there!
>I am currently having problems conjugating a hamster-anti-mouse CD3 mAb. 
All the 
>usual protocols are unsuccessful.  Anybody out there have any hints or
magic tricks?
>Any and all suggestions welcome.  Thanks!
I found some years ago that I could label anti-CD3 hamster Mabs (both I've
tried) by this procedure (that we use routinely for all Mabs):

Reductive Crosslinking of Antibody with Phycoerythrin

Reducing Buffer:  50 mM sodium phosphate, pH 6.0
         1 mM EDTA

Coupling Buffer:  50 mM sodium phosphate, pH 7.5
         1 mM EDTA

I. Maleimide labeling of PE

1) Exchange 3 mg PE into coupling buffer with PD-10 column
(pre-equilibrated with coupling buffer); chill on ice
2) Dissolve 1 mg sulfo-SMCC (Pierce) in 100 µl water; add 3 µl per mg PE.
3) Rotate gently for 1 hr at room temperature; foil covered
4) Isolate maleimide PE with PD-10 column (pre-equilibrated with coupling

II. Reducing antibody with DTT

1) Antibody at 1 mg/1 ml in reducing buffer (can dialyze or use PD10 column
or use Centricon concentrator)  
2) Add 1/50 vol 1 M stock soln of dithiothreitol (fresh in dist. water)
with mixing
3) Reduce for about 1 hour hour at room temperature; remove excess reagent
with PD-10 column equilibrated with coupling buffer

III. Forming crosslinked complex

1) Add 1 molar equivalent of SH-Ab to 1.5-2 molar equivalents of SMCC-PE
Example: for 0.5 mg antibody use 1.2-1.6 mg PE (more to taste)
2) Rotate for 3 hours to overnight
3) Add N-ethylmaleimide to block remaining free SH groups; 10 mg/ml DMF
stock soln (make fresh). Add 40 µg (4 µl) per mg Ab.  Rotate 15-30 minutes
at room temp
4) Pass down PD-10 column (equilibrated with Tris/Saline) or dialyze to
remove excess N-ethylmaleimide

For anti-CD3, I've never been satisfied with biotin/fluorescein conjugates. 
Hope it helps!
Richard R. Hardy          Member, Inst. for Cancer Research           
Fox Chase Cancer Center   Tel:    (215) 728-2463
7701 Burholme Ave.        FAX:    (215) 728-2412
Philadelphia, PA 19111    E-MAIL: RR_HARDY at

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