Introduction. A broken arm or wrist is usually caused by a fall onto an outstretched arm. It typically takes about six to eight weeks to heal in adults, and less time in children. Doctors refer to all breaks or cracks in bones as fractures.Go to your nearest accident and emergency (A&E) department if you think you or your child has broken a bone.t typically takes about six to eight weeks to heal in adults, and less time in children. Doctors refer to all breaks or cracks in bones as fractures. Go to your nearest accident and emergency (A&E) department if you think you or your child has broken a bone.
In contrast, the overwhelming majority of antigens for T cells are proteins, and these must be fragmented and recognized in association with MHC products expressed on the surface of nucleated cells, not in soluble form.
The macrophage is just one cell type that may present antigens in the MHCII complex; other cells, including B cells and dendritic cells, may also act as antigen-presenting cells (APC). Only a few helper T cells in the immune system will recognize the specific antigen presented by the APC.One helper T cell must become thousands of T cells to mount the immune response against the foreign invader. The animation illustrates the passage of signals through the cell that results in T-cell proliferation.he macrophage is just one cell type that may present antigens in the MHCII complex; other cells, including B cells and dendritic cells, may also act as antigen-presenting cells (APC). Only a few helper T cells in the immune system will recognize the specific antigen presented by the APC.