You may refer to the Biolegend's T cell isolation protocol.
It is Magnetic separation based.
https://www.biolegend.com/protocols/mojosort-isolation-kits-protocol-1/4599/
However, if you have access to a flow cytometer then you can also stain the splenocytes with CD3 and CD4/8 antibodies and separate by flow cytometry.
Isolation of splenocytes is pretty easy.
1. Mash the splenocytes on a 40/70 um cell strainer- fitted on a 50 ml tube, with a 3 ml syring plunger.
2. Wash the strainer with plenty of (15-30 ml) PBS to let cells pass through the pores of the strainer.
3. Centrifuge the cells at 1500 rpm in a swing bucket rotor, for 5 min.
4. Resuspend cells in 5 ml RBC lysis buffer (Ammonium Chloride- 4.01g, Sodium bi carbonate- 0.42g, EDTA- 18 mg, Water- 500 ml) and incuate at RT for 3 min.
5 Quickly add 20-25 ml PBS to stop further lysis of cells.
6. Centrifuge at 1500 rpm to pellet down the cells.
7. Resuspend in a suitable media and count the cells.
8. Follow the biolegend protocol.
Good luck,
Dear Sandeep,
If you're still looking for a protocol for T cell isolation from mouse spleen, I can recommend the CD3 Fab-TACS® Isolation Kit for mouse (https://www.iba-lifesciences.com/details/product/6-3404-004.html). Here you have the advantage that you can positively select you cells and in a final step remove the selection reagents again. So you get label-free, viable cells. You can find more infomation about the technology here: https://www.iba-lifesciences.com/fab-tacs.html