If you have vitamin d deficiency does it cause your t cells not to work?

I feel that vitamin D deficiency weakens your entire immune system as the vitamin D receptor is expressed in B cells, T cells and antigen presenting cells. Vitamin D's effect on the immune system has become very pronounced recently among the immunology specialists and especially since the covid pandemic.

Not specifically. Vitamin D is important for bone health, while it affects the body's response to infections, it is not specific to T-cells. For healthy diet: http://www.choosemyplate.gov/., exercise 30 minutes/day, drink enough water daily so your urine is mostly colorless, have safe sex, no tobacco alcohol weed or street drugs. Get HPV and Covid vaccines. Wish you good health!