From:Young Kwun

I use this same antibody (clone G168-15) and it works fine. What detection
system are you using? Since you have a faint staining, you can try a more
sensitive detection system such as Vector Elite. You can also try Dako's
high pH retrieval solution. You should dilute further than recommended (over
1:50) to minimize the tissue damage and microwave about 20-40 min. For
routine fresh large bowel case, I use microwave AR and Envision detection
system. However, for the archival cases, I retrieve the slides in citrate
buffer pH6.0 with pressure cooker for 10-15 min. And I use Vecta Elite
system for staining. I also do overnight incubation (1:600 dil) for archival
cases. After boiling I do not leave the slide for slow cooling!

Any small or large bowel tissue can be a good positive control, and HNPCC
cases showing microsatellite instibility (showing the loss of MLH-1 or MSH-2
expression at the neoplastic epithelium) are not uncommon from our
I hope this helps.

Young Kwun
Senior Hospital Scientist
Dept. of Anatomical Pathology
Concord Hospital
Concord NSW 2139 Australia

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> -----Original Message-----
> From: Klassen, Shannon SDH []
> Sent: Wednesday, 13 November 2002 02:32
> To: 'Histonet'
> Subject: MLH1
> Need help ASAP with MLH1 - BD Pharmingen #554072 - pretreatment
> /dilution/control? - Can't get it to work well - nuclear staining
> there but
> weak , and I can't take the dilution any lower. Thanks in advance.
> Shannon Klassen
> IHC Tech
> Regional Health Authority #6
> Saskatoon, Canada
> 306 655 8569

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