Answer to Question #216782 in Microbiology for Nizba

Question

describe activation of CD4 helper T cells by interaction of the TCR with peptide fragments presented by class II MHC molecules on APCs

Answer 1

In at least two important ways, T cell responses differ from B cell responses. First, T lymphocytes in peripheral lymphoid organs are only triggered by foreign antigens to proliferate and develop into effector cells when the antigen is shown on the surface of antigen-presenting cells. T cells react in this way because the antigen they identify isn't the same as the antigen recognized by B cells. T lymphocytes recognize fragments of protein antigens that have been partially degraded inside the antigen-presenting cell, whereas B cells recognize the full antigen. In at least two key ways, T cell responses differ from B cell responses. T cells are only activated to proliferate and develop into effector cells when foreign antigen is shown on the surface of antigen-presenting cells in peripheral lymphoid organs. Because the type of antigen detected by T cells differs from that of B cells, they respond in this way. T lymphocytes recognize antigen fragments that have been partially degraded inside the antigen-presenting cell, whereas B cells recognize the complete antigen.

T cells are divided into two types: cytotoxic T cells and helper T cells. Cells infected with a virus or another intracellular pathogen are immediately killed by effector cytotoxic T cells. On the other hand, effector helper T cells aid in the stimulation of other cells, including macrophages, B cells, and cytotoxic T cells. Finally, T cells are being explained in the thymus, selected during development to ensure that only cells with potentially relevant receptors survive and mature. To begin, we must consider the characteristics of the antigen-recognition receptors on T cells' cell surfaces.