Looking for a bored immunologist

February 28, 2007 11:59 AM

Any research immunologists out there? I need information on footpad swelling experiments in mice.

I'm a geneticist and molecular biologist by trade--so pardon my ignorance, but I don't have any immunologists in my new lab to ask my dumb questions anymore. What exactly is footpad swelling in a mouse model indicative of? Why would you use this particular measurement versus something else?

I'm presenting a journal club on Friday, so I can describe the data if it makes any difference.

posted by divka to science & nature (14 comments total)

IANAI, but it seems to be a way to measure inflammation and/or edema, as in the case of an infection. I think a lot of these types of assays are used for historical reasons and to facillitate comparison with older experiments.
posted by exogenous at 12:13 PM on February 28, 2007

from here

Our findings that anti-IL-12 abrogated control of parasite growth in the lymph nodes of C57BL/6 mice is in contrast to a previous report in which anti-IL-12 treatment did not alter control of secondary infection (as assessed by footpad swelling) in a different resistant strain (C3H) of mouse (22).

Seems to indicate infection, but IANAI.
posted by jourman2 at 12:19 PM on February 28, 2007

Hmm, further staring at the paper seems to indicate that in this particular experiment they claim the footpad swelling is indicitive of T-cell response...If this sounds totally off course, let me know.

I wish they would stop sneaking immunology into these nifty genetics papers. (Just kidding, of course).
posted by divka at 12:21 PM on February 28, 2007

I was under the impression that edema was more related to the innate immune response (cytokines increasing the permeability of vessels) than the adaptive (T/Bcells). But I'm looking into it some more...
posted by twoporedomain at 12:57 PM on February 28, 2007

Ignore my previous answer. The foot-pad swelling was referred to as a measure of "delayed type hypersensitivity" by this paper (PDF available with subscription), and a subsequent pubmed search brought up this abstract, which summarizes the role of T-cell response. Maybe an ISI cited reference search on that review will be useful for getting more up-to-date info.
posted by twoporedomain at 1:11 PM on February 28, 2007

IANARI, but I am a grad student. The odds are good that they cite another paper when they talk abotu footpad swelling, either in the methods, or in the results/discussion. Backtrack through the sources, skim a few papers and see what you can find out.

Or, take the lazy man's approach and use google scholar or pubmed to find relevant papers that may have better explanations.
posted by chrisamiller at 1:14 PM on February 28, 2007

Is the footpad inflammation a tool? To measure pain sensitivity? (neuroscientist here, so that's the only time I see footpad inflammation stuff). Could you cite the paper you're presenting?
posted by gaspode at 1:26 PM on February 28, 2007

I am an immunology Masters, if that helps and the paper reference would be helpful for exactly what they're trying to show. Footpad injections are good for DTH responses (as mentioned above). Basically, from what I've been exposed to, a mouse is infected with a primary pathogen and then is re-exposed to the antigen in question in the footpad. The swelling is measured over time with calipers and graphed vs. the appropriate control to measure the speed and intensity of the immune response to the antigen. This is usually accompanied by lymph node analysis (either removing them and reculturing the cells or phenotyping them directly).

A human corollary is the TB skin test.

At the very least, papers from the Scott lab (University of Pennsylvania) use this model to study leishmaniasis. A quick PubMed search for Phil Scott and his cohorts should help out with data, materials/methods and interpretations.
posted by oreonax at 1:32 PM on February 28, 2007

Sure, this is the paper that generated the data (it actually was in a review I was using to structure a literature review. It isn't *quite* a journal club--but close enough):

Figure 5 in this paper

Basically, all I need is a one sentence description since no one else in my audience is an immunologist either. The "DTH" description is probably enough. I just hate presenting data that I don't entirely understand.
posted by divka at 1:54 PM on February 28, 2007

IANAI, but I'm pretty sure oreonax has it. The primary pathogen is C. neoformans cells (see Methods, Animal Studies) and the antigen used to test the developed immune response is a dialyzed supernatant from a broth of C. neoformans (see Methods, Delayed-type hypersensitivity response assay).


It is not a pain sensitivity assessment.
posted by mbd1mbd1 at 3:48 PM on February 28, 2007

Delayed type hypersensitivity is also known as the type IV immune response. It's the one you're usually thinking of when you think of a serious drug allergy, for instance.
posted by ikkyu2 at 5:36 PM on February 28, 2007

I am a research immunologist (finally, my day has come!), and oreonax does have it. I will emphasise that DTH responses are antigen-specific responses and are therefore T cell-dependant. Therefore, DTH is used as a measure of T cell memory responses.

Footpad swelling experiments are a crude way of looking at T cell memory to a particular antigen. And I say crude, because most of the time, footpad swelling isn't measured in a blinded fashion, and people tend to get the results they are looking for regardless of whether the result is true - due to unconscious bias, the control animals feet tend to get squeezed a bit more with the calipers than the treatment animals, resulting in exaggerated differences.

If you want a basic break-down of what's happening for your JC, here goes:

T cells can be broken down into two subtypes - naive and memory (forget the CD4 CD8 subtyping, you don't need to know about it). All T cells start out as naive T cells. Naive T cells can only travel in the blood and lymph. Not into the skin (they're missing the adhesion molecules on their cell surface that allows the to leave the blood into the peripheral tissues). They rely on dendritic cells to deliver the antigen - in this case purified cryptococcal antigen (CneAg) - to the draining lymph nodes before they can divide and turn into memory T cells. This process takes a number of days.
Memory T cells can travel everywhere. They can go into the skin, and when they see the antigen (which they have already seen at least once before when they were naive T cells), they initiate a local inflammatory response - basically, they secrete a lot of cytokines that causes a cascade of events, such as increasing macrophage activity and recruiting neutrophils etc.
If a mouse has never seen the antigen before, it will take days before memory T cells appear. So there will be some innate, non-antigen specific inflammation going on for the first 48hours, but not much.
Now if the mouse has seen the antigen before, it will already have memory T cells that will be circulating the skin, and it will see and respond to the antigen in a matter of hours. This means the degree of inflammation will be markedly higher in those first two days.

Like people, some strains of mice have better DTH responses than others. C57/BL6 mice have the best responses. Balb/c mice have shit responses (I think!), and I suspect that C3H's are more similar to Balb/c's in this respect.

Hope this helps :-)
posted by kisch mokusch at 9:55 PM on February 28, 2007

I have asked for the paper and have not read it as it seems that kisch mokusch has done so and explained it very well.

So my last two cents is this, if you want a one sentence description of what people mean when they put up footpad data:

Increased footpad size correlates to a greater antigen specific immune response.
posted by oreonax at 6:27 AM on March 1, 2007

Update: thanks all for your input. Predicatably, somebody *did* ask me to go into more detail on this experiment during my journal club and I was able to ramble on like I knew what I was talking about.
posted by divka at 9:57 AM on March 6, 2007