After all, a nail is sharp, and the inside of the nose is sensitive. Putting a foreign object deep into your nasal cavity isn't particularly comfortable, and it can be certainly painful when the performer is learning to do the trick. However, another obstacle -- sneezing -- can be harder to overcome.
Osteoclasts are the bone cell that destroys bone. This allows bone  remodeling, and allows the skeletal system to act as a reservoir  for minerals to maintain blood mineral â¦ levels. Bone cells that are involved in reabsorption and breakdown of the  bone matrix are referred to as osteoclasts.
MHC II are the special molecules that are only expressed in antigen-presenting cells, which I think is what you are referring to. As neither CD4 or CD8 T-cells present antigens, they do not express MHC-II themselves.