What exactly are CD4+3- inducer cells? - simply a specific form of "T-helper-cells"? (Nov/16/2008 )

I am to give a presentation about this article http://jem.rupress.org/cgi/content/abstract/204/6/1267.
I've seen the term "helper/inducer t-cells", which leads me to the conclusion that being CD4-positive, CD4+3- inducer cells probably simply are a type of t-helper cells which happen to be CD3-negative and induce the maturation of mTECs (as shown in the article).

As I'm not a 100% sure whether the term may actually define cells that induce the development of CD4+3- cells, I decided to make a post here!



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There are other things about the article I have bigger dificulties in understanding for now. The toughest one is:
In order to provide evidence for a precursor-product relationship between CD80- and CD80+ mTECs, the following steps were taken:

"purified Lys51- EpCAM1+ CD80- mTECs from 7-d H-2b fetal thymus organ culture (FTOC) were mixed with disaggregated fetal thymus suspensions from MHC-mismatched H-2d embryos at a 1:5 ratio. Chimeric reaggregate thymus organ cultures (RTOCs) were cultured for 2 d, disaggregated, and analyzed by flow cytometry."

now what does the MHC-mismatched tell me? I really can't quite grasp what kind of RTOCs we get here. A mix of CD80- mTECs and... what exactly? How are these RTOCs gonna help me prove a precursor-product relationship?

(the text goes on: "Fig. 1 shows the introduced 1Ab+ donor-derived cells persist over this period, and in contrast to the outset of culture when introduced mTECs were CD80-, a proportion of 1Ab donor-derived mTECs are CD80+")

--> so there is a way of knowing the CD80+ mTECs found in the end were not initially part of the thymus suspensions from MHC-mismatched embryos but are "1Ab donor-derived" mTECs which were originally CD80-. I don't actually happen to understand how we know that, though!

Hopefully your presntation has not come and gone ...

You have come across a very elusive cell type (and extremely interesting paper) that is quickly gaining ground in current immunology. Upon first glance, the CD4+CD3- subset was initially identified as activated CD4+ T cells. Further examiniation of this cell type, via some very clever experiments, actually described that they were more closely related to DCs! Subsequent experiments, have indeed shown that they are a DC population (that surprisingly is very poor at promoting T cell activation).

The primary function of this subset of DCs is not entirely understood, but recent data has indicated that they are important in supporting lymphoid tissue architecture. This phenonmen is sufficiently addressed in the paper you are presenting, specifically in the thymus. Other functions for this subset include providing help to T cells, which in turn can promote B cells to undergo affinity maturation in germinal centers.

If you haven't presented this paper yet and still need help understanding or interpreting the data presented in this paper let me know and I can try to help you.

I forgot to mention, that there is a relatively recent review in Nat. Imm. from JP Lane's group in the UK. This would be provide an excellent introduction to your presentation.