00:01
So, in this question, we have to explain t cell development that how do the lymphoid progenitors, they develop into mature t cells.
00:10
So, firstly, we know that t cell development, it occurs in the thymus.
00:15
So, firstly, we have in the bone marrow certain hematopoietic stem cells and some of these hematopoietic stem cells, they become committed to form the t cells and these cells are known as the lymphoid progenitors.
00:31
The lymphoid progenitors and these lymphoid progenitors they will migrate to the thymus and in the thymus they will acquire an environment and then in the thymus these lymphoid progenitors they will develop into dn cells dn cells are basically double negative cells so these are the double negative cells double negative meaning they don't have the cd4 cd4 receptor is also absent and cd8 receptor is also absent now after the dn stage what happens is in the dn stage there is a stage named dn1 to dn4 and in the dn3 stage in the double negative 3 stage what happens the beta chain of the t cell receptor rearranges.
01:32
So there is beta chain gene rearrangement which is happening in the dn3 stage.
01:42
And after beta chain rearrangement, a functional beta receptor or beta chain is arranged.
01:51
And this beta chain it will couple with the pre -t alpha chain and this whole complex of beta chain plus pre -t alpha chain is known as the pre -tcr complex or the pre -t cell receptor complex.
02:14
Now after forming this complex this dm3 stage will convert into a double positive stage.
02:22
So double positive stage which is basically dp...