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Sda ?


KatarinaN

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Hi!

 

We have had mysterious samples that all are reacting weakly, medium or strongly, some with papainised cells and others not and also some in room temperature and others not. We had an answer that it is Sda that is bothering us. 

 

Can anyone tell me anything about Sda and/or anti-Sda? It is quite hard to find info about this antigen and antibody and this is totally new thing for me (haven't heard about it at all).   :confused: Any good articles?

 

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Thank you! Later I discussed this with our head of department and he remembered that in "the old days" there used to be quite much anti-Sda but it has disappeared since gel technique. And I start to ask about that guinea pig urine (Malcom, what is so special in guinea pigs urine that for example cats urine can't do the trick?) since one of my collagues has one..  :whew:

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The easy ones first eh KatarinaN!!!!!!!!!!!!!!!

 

It was something I remembered from way back (early to mid-1970's), when I first worked at the International Blood Group Reference Laboratory (I went back there again for a short time as a locum).

 

Guinea pig urine is specifically mentioned on page 402 of Race RR, Sanger R.  Blood Groups in Man.  6th edition.  1975.  Blackwell Scientific Publications.

 

I think it came from a paper they cited:  Morton JA, Terry AM.  The Sda blood group antigen.  Biochemical properties of urinary Sda.  Vox Sang  1970; 19: 151-161, but I would have to check that.  I do remember, however, that we used to keep a supply of frozen guinea pig urine for inhibiting anti-Sda, so, presumably, this worked better than other sources of urine.

 

As an aside, do you know that Sda was originally named Sid? It was named this after Sid Smith, who used to be the janitor at the Medical Research Council's Blood Group Unit, when it was in London, as he had the strongest expression of the antigen at the time it was identified.  In those days, antigens and antibodies were usually named after the first two letters of the surname of such a person, but Sm was already being used for the antigen within the Scianna Blood Group System, that is now known as Sc1, so they named it Sid!!!!!!!!!!

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As an aside, do you know that Sda was originally named Sid? It was named this after Sid Smith, who used to be the janitor at the Medical Research Council's Blood Group Unit, when it was in London, as he had the strongest expression of the antigen at the time it was identified.  In those days, antigens and antibodies were usually named after the first two letters of the surname of such a person, but Sm was already being used for the antigen within the Scianna Blood Group System, that is now known as Sc1, so they named it Sid!!!!!!!!!!

 

 

I love these "Oh, by the way...." stories!  Thanks!

 

Donna

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My guess is that all of the reactivity you have discribed is not due to Sda  antibodies exclusively.  I've been working in a Reference Lab since 88' and I can count on one hand...maybe a hand and a half, the number of anti-Sda antibodies I've worked on. 

 

As David mentioned, the agglutination is very distinctive: when observed microscopically, they can appear as tight (globs) refractile agglutinates "in a sea of free cells" (as the Antigen Facts Book mentions).

 

Most that I have worked on were detected at AHG, and most often micro reactions or very weak macro.  Very seldom at RT which goes against what the Antigens Facts Book states (not saying that info is wrong).  The reactivity is enhanced when tested with enzyme-treated red cells and personally....I'd send it to a Reference Lab prior to collecting that guinea pig urine from your collegue's pet.  Just sayin.... B)

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My line was always as hard as it is to catheterize a guinea pig, it's even harder to train them to pee into those little cups.........

 

The procedure in the tech manual says to use freshly collected urine and boil it first. Do any of your reference lab types (ahem Malcolm) know what this step is for? It sounds like the start of a secretor study, where the boiling inactivates salivary enzymes that might start to digest your soluble blood group substances. I have happily used pooled urine from 5 or 6 urines with a neutral pH and it seems to work just fine without the boiling, and without dialyzing for that matter. Any danger in this?

 

Thanks - Phil

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I came across a patient years ago that had a strong anti-Sda. The first thing I noted was that very distinctive appearance of the agglutination. I decided to try urine inhibition for giggles and it worked great. As mentioned above, a pooled sample from 6 different donors will neutralize the antibody and doing that to my patient's sample totally removed the antibody activity. I did not dialyze or boil the urine - though we did still have bunsen burners in the lab so I could have boiled it...ick.

 

Unlike the rest of the clinical lab, blood bankers can still have fun playing with stuff we read in books - how cool is that!

Edited by AMcCord
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As an addendum, what we do with anti-Sid (love the janitor story by the way) is:

  • Look for the unique "Sidish" appearance
  • Try to eliminate other ab choices per routine panel techniques
  • Do the urine neutralization on all reactive reagent cells to make sure the rxn go away with the urine but stay with the dilutional control.
  • Find full XM compatible units with straight serum/plasma - usually not too hard.

Many panel manufacturers will also indicate cells that are strongly Sd(a+) which can be a clue to what you're dealing with.

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Maybe in Ortho Cassettes, but in BioRad cards, no.  Your reaction looks more like an IgM antibody reacting with one cell (an anti-M??)   (I am presuming single donor cells, not pooled)

 

They are Ortho cards. Repeat sample was dual pop in all 3 cells. I've started a thread about it as I am bemused....

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 Hi All,

 

The reference UI quoted in post 7 was not the one I thought it was.  It was a VERY complicated paper explaining the biochemistry behind the inhibition of anti-Sda, and I didn't understand a word of it!

 

I have, however, tracked down another, later paper that explains why it is Guinea-pig uring that is used, rather than urine from other species (although human urine does contain an inhibitor.  It is still not the original paper, but it may be of interest.  It is:

 

Serafini-Cessi F, Dall'olio F.  Guinea-pig kidney beta-N-acetylgalactosaminyltransferase towards Tamm-Horsfall glycoprotein.  Requirement of sialic acid in the acceptor for transferase activity.  Biochem J 1983; 215: 483-489.

 

I believe that Guinea-pig kidney is rich in Tamm-Horsfall glycoprotein, BUT, have a care KatrinaN.  For their experiments, the authors beheaded the Guinea-pigs and then dissected out the kidneys.  I would suggest that, if you did this to your friend's Guinea-pig, you would be one friend down!!!!!!!!!!!!!          :fear:  :fear:  :fear:  :fear:  :fear:

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