Hello, I have used SEB for T cell stimulation but SEB binds to MHC II and TCR, why is it so potent to simulate purified T cells not PBMC without any APC in it? T cells do not express MHC II right? Anything explained that I missed? Thank you in advance. I use human T cells from PBMC, not mice.
Thank you Lora, so that means some (naturally or for some reason) activated T cells with MHC II activate other T cells and they express MHC II as well, then SEB works for all. Is that right?
yes. SEB is binding the Vbeta of one T cell to the MHC-II on another T cell.
Probably you were taught that only macrophages, DC and B cells express MHC-II, as well as endothelium. Paradigms are taught in class, there is a body of literature from 20+ years ago that addresses MHC-II on human T cells. A good paper that examines the mechanics of this using primary human T cells and Jurkats can be found: https://www.jimmunol.org/content/168/2/763
I see, this is a good paper to understand how MHC II molecules are differently expressed on different cells. Thank you! Yes, although I assumed not exclusive, I always thought major population to express MHC II are the APCs but knew SEB works purified T cells so was confused. I wonder if anti-CD3/CD28 is more physiological for purified T cell activation than SEB.. Also, this paper only tested CD4 not CD8, do you know the reason?
Hi Yumi, I have not compared the 2, but conceptionally, let me explain: anti-CD3/CD28 Tx should activate all T cells, where as SEB will only activate a subset of T cells that have Vbeta5. The frequency of Vbeta5+ T cells varies in the human population based on immunogenetics of the host, infection and disease state. Thus, if you are analyzing between different human subjects, you should use anti-CD3/CD28 to control against the variables.
Hi Lora, we just missed each other.. I edited my reply!! I used to use anti-CD3/CD28 but now the project inherited, it was SEB so I stick with it. SEB is so much more potent than anti-CD3/CD28 though, even though it only works for subsets of the T cells.. any thoughts?
For short term restimulation, such as for ICS, you only see activity in antigen-experienced cells. If you use SEB in infants, many will have a lackluster response because of the paucity of antigen-experienced cells.