Cytokines in Adaptive Immunity

00:02 In adaptive immunity, cytokines are going to be very important mediators.

00:06 So I've used the term a couple times, let's just describe what these really are.

00:11 So they are made by a variety of cell types, but I'm going to emphasise the ones here made by CD4 helper T cells, since that's their major job making cytokines.

00:23 The first cytokine that is made usually after interaction with an antigen presenting cell, showing displaying a foreign peptide is Interleukin-2 or IL-2.

00:34 IL-2 is very important because it causes clonal expansion of that T cell, a single T cell can't do very much, you need a clonal army to deal with infections.

00:45 So the very first cytokine that's made is IL-2, which in that local environment will drive in an autocrine pathway, a feedback loop.

00:55 It will drive the proliferation of the responding T cells, so we get more and more and more of them.

01:01 That's a good thing because we need a clonal army to do it's job.

01:06 That clonal army will also make other cytokines such as interferon gamma.

01:11 Interferon gamma has a variety of effects.

01:12 But the most important one for this discussion right now is the activation of macrophages.

01:17 We will turn macrophages into Macrophages, from someone who looks like me into Arnold Schwarzenegger at his peak, so they become much more aggressive killers, and they will do their job better.

01:30 Other cytokines that are produced by the activated T helper cell include those that will drive specific B cell activation and will lead to the elaboration of specific isotypes.

01:42 So those T cells, the helper T cells in our clonal army are going to make interleukin-2, interleukin-4, interferon gamma, interleukin-5, all of which will affect B cells and tell them which antibodies are going to be most important.

01:59 In addition, cytokines, such as interleukin-2 and interferon gamma will drive the activation of cytotoxic T lymphocytes.

02:08 So I hope you're getting the idea that the helper T cell through the elaboration of a variety of cytokines can drive a whole bunch of both innate and adaptive immune responses.

02:20 So in words, kind of what I've just said in the figure form on the right.

02:24 These cytokines are made by CD4 helper T cells.

02:26 It's important to also understand that cytokines can be made by CDA positive cytotoxic T cells or by natural killer cells or by macrophages.

02:35 So, there are a variety of cytokines made by different cell types.

02:41 Those cytokines will activate cells of innate and adaptive immunity.

02:45 And they will regulate B cell isotype selection and B cell proliferation, the activation and proliferation of cytotoxic T lymphocytes, the activation of macrophages, of NK cells, of endothelial cells etc.

03:01 So, there are a tonne of effects related to these protein mediators coming out of an activated T cell.

03:10 Most important T cell for these CD4-positive, although other cell types can do it.

03:16 And with that, we've concluded a brief run through of adaptive immunity.