Cluster(s) of Differentiation

[helpfulstranger]

Is there a good list where I can find the important ones for Step I?

Here are some culled from wikipedia that I guess might be important

CD1 - histiocytes. Important in Langerhans histiocytosis
CD2 - T cells, NK cells
CD3 - T cell receptor
CD4 - MHCII coreceptor (macs, helper T cells) - mycosis fungoides
CD5 - mantle cell lymphoma and T cell lymphomas
CD8 - MHCI coreceptor (cytotoxic T cells)
CD10 - common ALL antigen (cALLa). Important in ALL.
CD11c - integrin (dendritic cells) - hairy cell leukemia
CD14 - macs
CD15 - a carbohydrate that plays a role in phagocytosis and chemotaxis (neutrophils) - Reed Sternberg cells
CD16 - binds Fc of IgG - NK
CD18 (LFA-1 integrin) - defective in leukocyte adhesion deficiency
CD19 - B cell coreceptor
CD20 - B cells - target of rituximab
CD21 - cytoplasm of pre B cells, cell surface of mature B cells - receptor for EBV
CD27 - plasma cells
CD28 - costimulatory molecule required for T cell activation
CD30 - Reed Sternberg cells
CD31 - PECAM-1 - seen in liver angiosarcoma
CD33 - AML blasts
CD34 - stem cell marker
CD40 - APC (including B cells) costimulatory molecule
CD40L (CD154) - T cell costimulatory molecule
CD45 - all hematopoietic cells except RBCs
CD54 - ICAM1
CD56 - NK cells
CD55 - DAF - inhibitor of complement membrane attack complex - absent in PNH
CD59 - MIRL - inhibitor of complement membrane attack complex - absent in PNH
CD80/86 - B7 coreceptor on APC - key for T cell activation
CD117 - cKit (mast cells) - GIST


other possibly useful cell type signatures:
fibrocytes in graft rejection - CD34+ CD38-
Tregs - CD3+ CD4+ CD25+ and Foxp3+

[edits] I have already heard 2 people say that they had a question about Foxp3 on their exam.

As far as CD32 goes, I wasn't really sure about it's relationship to GMCSF, so I left it out for now. If anyone can find a reference I will gladly add it in.

Please add in any others that I have missed or correct any mistakes I might have made.

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[beeitchness]

they're in FA

 

[helpfulstranger]

I said a good list. The one in FA is (with all due respect) a bit simplistic.

 

[HelpPleaseMD]

Your missing CD 16. CD 28. CD 95. And probably some others. thats all i can think of off the top my head

O and CD 59. that one is important

 

[helpfulstranger]

Just added those in. Thanks for your suggestion HelpPleaseMD!!

 

[AndyRSC]

A few more for you:

CD1 - histiocytes. Important in Langerhans histiocytosis.
CD10 - common ALL antigen (cALLa). Important in ALL.

 

[helpfulstranger]

Updated. Thank you Andy RSC.

 

[tco]

If you're really interested, pathologyoutlines.com has many of them.

There's a reason that FA is simplistic in how many CDs it has listed - they're very low yield. Yes, they are important if you're going to become a hematopathologist, but not if you're going to become a MSIII.

 

[usmleq]

I said a good list. The one in FA is (with all due respect) a bit simplistic.

The ones in FA are a good list for Step 1. If you want more, maybe try the pathology forum

 

[DroptheBop]

CD18 (LFA-1 integrin) - defective in leukocyte adhesion deficiency

 

[Go Ducks]

I'd suggest using FA and adding any from UWorld that you run across. Seriously, I think the OP's list is overkill. The FA list is simplistic because your knowledge can be simplistic in this area. For example, you won't have to identify AML blasts by their CD number alone. They will give you the auer rods or the (15;17) translocation.

 

[AndyRSC]

Most of that list is actually in FA, just scattered across different sections (immuno, heme/onc, etc.).

 

[Phloston]

I'd suggest using FA and adding any from UWorld that you run across. Seriously, I think the OP's list is overkill. The FA list is simplistic because your knowledge can be simplistic in this area. For example, you won't have to identify AML blasts by their CD number alone. They will give you the auer rods or the (15;17) translocation.

This list isn't overkill at all. These are most certainly up for grabs with respect to some of the wtf-questions.

Helpfulstranger, I'm glad you posted this btw.

Going off the top of my head here:

I've also seen CD31 in a question (PECAM-1). It took me a while not to get this mixed up with ICAM-1 (CD54).

As far as CD2 is concerned, I had seen that in a question worded along the lines of, "which of the following is the marker seen on all thymocytes?" I believe I had encountered that in Kaplan QBook, but I'm not 100% sure. That also possibly means it's seen on dendritic cells, since those mature in the Hassall's corpuscles of the thymus.

I've also seen CD27 in a practice question. That's a marker for plasma cells. This question was worded along the lines of, "which of the following is most closely related to hyper-acute graft-rejection?" Plasma cells --> preformed Abs. I believe I saw that in USMLE Rx. If the USMLE writers wanted to be ridiculous, this could also be used for a multiple myeloma wtf-question.

About the CD34 marker for stem cells, I've also seen that in a practice question as a marker for fibrocytes, so that's also seen in chronic graft rejection.

For stem cells, not fibrocytes, however, I had seen that they're CD34(+) and notably CD38(negative).

And I also recall having seen CD32 in a practice question. It responds to GM-CSF. I just remember IL-3 and CD32 for GM-CSF.

CD25 is also not on this list. This is the regulatory T-cell marker (Tregs). Someone had posted on this forum a couple weeks ago about having seen a Treg question on his USMLE. Well, Tregs = CD3, 4, 25, and Foxp3. FA mentions CD25 I believe, but it doesn't mention Foxp3.

On your list, you have CD45 for all haematopoeitic cells except RBCs. I had seen CD45 in a question asking about lymphomas. Apparently all lymphomas are CD45 positive. This matched what you've written, but for some reason, the question I had seen framed it within the context of lymphoma.

Hope that helps,

 

[ijn]

Step 1 isn't an immunology board exam. FWIW I got one CD question out of 322 questions, and it was one of the high yield / easy ones. Don't waste your time beyond First Aid unless you're running out of things to study.

 

[Go Ducks]

This list isn't overkill at all. These are most certainly up for grabs with respect to some of the wtf-questions.

I'm not saying that those numbers won't pop up in question stems. I'm saying that you won't have to know them in order to answer the question. There won't be a question saying, "You see cells marked with CD34, what's the process?" and have to answer, "chronic rejection." Instead, it will give you a history that points to chronic rejection which might mention the CD34 cells but won't be reliant on them.

Of course, you'll have to know the obvious ones but those are covered throughout FA.

That said, if this is how you feel like spending your time, knock yourself out. I'd rather be memorizing all those damn drug side effects.

 

[Phloston]

Step 1 isn't an immunology board exam. FWIW I got one CD question out of 322 questions, and it was one of the high yield / easy ones. Don't waste your time beyond First Aid unless you're running out of things to study.

I'm not saying that those numbers won't pop up in question stems. I'm saying that you won't have to know them in order to answer the question. There won't be a question saying, "You see cells marked with CD34, what's the process?" and have to answer, "chronic rejection." Instead, it will give you a history that points to chronic rejection which might mention the CD34 cells but won't be reliant on them.

Of course, you'll have to know the obvious ones but those are covered throughout FA.

That said, if this is how you feel like spending your time, knock yourself out. I'd rather be memorizing all those damn drug side effects.

I wish this weren't the case, but I disagree with both of you here.

Wtf-questions happen to everybody. This list is not hard to just memorize, and out of the 7000+ practice questions I've done already, I've encountered 3 or 4 that required pure knowledge of a CD# not in FA, without assistance from the question stem. That means if we were to sit the USMLE several times over, we would eventually hit one of those wtf-questions. Fortunately, we don't have to sit it more than once, but what it does mean is that somebody reading this will get assessed on the material accordingly.

 

[ijn]

Just because you saw it in a third party question bank does not mean it's actually a STEP 1 level question or STEP 1 relevant material. You put too much faith in those sources. They're tasked with writing a huge volume of questions, not necessarily relevant STEP 1 questions.

I can't recall any CD or interleukin not in First Aid being asked between 600 CBSE questions, 2000 CBSSA questions, the 150 yearly released items, and the 322 STEP 1 questions that I've been exposed to. Goljan claims CD10 was on some student's exam, so I guess that one is worth learning. First Aid acutally has CD 10 in it but they just call it CALLA without making the connection to the CD number.

 

[Phloston]

Just because you saw it in a third party question bank does not mean it's actually a STEP 1 level question or STEP 1 relevant material. You put too much faith in those sources. They're tasked with writing a huge volume of questions, not necessarily relevant STEP 1 questions.

I can't recall any CD or interleukin not in First Aid being asked between 600 CBSE questions, 2000 CBSSA questions, the 150 yearly released items, and the 322 STEP 1 questions that I've been exposed to. Goljan claims CD10 was on some student's exam, so I guess that one is worth learning. First Aid acutally has CD 10 in it but they just call it CALLA without making the connection to the CD number.

That logic doesn't really make sense. You can't say one is worth learning and the others aren't. Honestly though, if you (or anyone else) don't want to spend the 5 minutes to just memorize them, then don't. Not everyone will be prepped for wtf-questions on the exam. If everyone were prepped, then the average would be 260.

 

[ijn]

The logic makes perfect sense. Goljan provided anecdotal evidence that a specific CD (which he thought was previously low yield) was on an actual STEP 1 question. I haven't heard anyone put forward evidence that some of the random CDs such as 32/33 that you listed have ever been tested.

I mean great, learn them, but you'd probably get more bang for your buck on "WTF" questions by studying up on STEP 2 CK level material (best diagnostic test, next step in management, common STEP 2 pathologies not mentioned in First Aid, etc.) which seemingly can appear on STEP 1.

 

[MrBeauregard]

The logic makes perfect sense. Goljan provided anecdotal evidence that a specific CD (which he thought was previously low yield) was on an actual STEP 1 question. I haven't heard anyone put forward evidence that some of the random CDs such as 32/33 that you listed have ever been tested.

I mean great, learn them, but you'd probably get more bang for your buck on "WTF" questions by studying up on STEP 2 CK level material (best diagnostic test, next step in management, common STEP 2 pathologies not mentioned in First Aid, etc.) which seemingly can appear on STEP 1.

Absolutely. There were times I was studying Goljan that I sort of glossed over the last bullet point in each category dealing with diagnostic testing and/or treatment. Those questions are actually fair game on Step 1. Although, if you understand the disease process pretty well you can reason it out with fair certainty.

Phloston, I sat my exam this past Friday. The "WTF" questions (I can't believe that has become a question category on SDN recently) weren't questions dealing with obscure details but were more questions that required the student to understand the concocted experiment, carry it out in their head, and then interpret the results and answer some question regarding the results/experiment/connected detail/underlying concept. Granted, I did have some detailed molecular/cellular biology questions dealing with the nuclear membrane, but I knew these from junior year undergrad (crazy I had to reach that far back to answer a medical school licensing exam question) and not from studying during dedicated time or during medical school. If I could advise you on what to do, although I believe you will do very well with any random form you receive, I would say that you should attempt to prepare yourself for bizarre experiments by developing a true understanding of material. While memorizing long lists of drugs not found in FA or UW or an exhaustive list of every cluster designation may get you a single point on your exam (literally), making sure you understand material on the most basic level will ensure that you get maybe 5 questions. To me, this seems like more bang for your buck. I'm a lot like you and I love the details, but after sitting the exam, it became clear that Step 1 isn't a test about details; it's big picture. Sure there are some that want that detail, but the majority of them (on my test at least) simply wanted me to answer "myocarditis" or "immune-complex deposition". Pretty non-specific and big picture thinking. If the concepts aren't there and the ability to connect dots across systems is absent, no amount of detail memorization will get you the correct answer to a question. Just keep sight of the forest.

Just FYI, I didn't have a single CD question on my exam, and every single pharmacology question was extremely straightforward, mainly asking for MOA. I think I had two questions asking for a drug to treat, and it was the prototype or the protoclass (is that a word?).

 

[shenanigi]

Didn't have a single CD question yesterday

 

[spyderracing32]

The only ones that weren't explicitly in FA that I saw come up with any frequency in the Q banks (and I actually saw them on my CBSE) were CD55 and 59 (DAF and MIRL). Basically, if it's a key player in any kind of pathology, you'd be best to know it and know why it's relevant. For instance, you have CD21 listed up there as being in the cytoplasm of pre-B cells but on the surface of mature B cells, but most importantly it is the port of entry for EBV into B cells (and come to think of it I may have seen a CD21 Q on my exam, but I also saw that a few times in Q banks so I could be wrong).

 

[helpfulstranger]

Admittedly, this isn't the high-yieldiest of high-yield 8 star topics. But I thought it might be nice "salt and pepper" to have in making a decision on a tough question. Thanks to all who have contributed so far.

 

[HelpPleaseMD]

CD 52. target of alemtuzumab for CLL