What immunoglobulin is expressed on the surface of B cells that identify them as immature? mature? Explain it.

Dendritic cells are phagocytic, but also capable of ingesting large amounts of extracellular fluid and its contents, a process known as macropinocytosis. What specialized function do dendritic cells have in immunity that might account for their need to perform macropinocytosis?

The immune system involves both the humoral and cell-mediated branches. It is known that T cells can perform a range of different functions once selected by antigen encounter, including secretion of soluble compounds to aid other white blood cells, such as B lymphocytes. If T cells can aid the function of B lymohocytes, then is it incorrect to say that both branches of the immune system (humoral and cell-mediated) involves B cells? I ask this question because I commonly hear that humoral immunity involves B cells rather than both branches.

In what way does the T cell’s membrane receptors differ from the B cell’s membrane receptor? In other words, what will each bind to?