GFAP and desmin expression in lymphatic tissues leads to difficulties in distinguishing between glial and stromal cells.

Recently, we found many immune cells including antigen presenting cells neurally hard wired in the T-cell zone of most lymphoid organs like amongst others, lymph nodes in rats, mice and humans. Single immune cells were reached by single neurites and enclosed with a dense neural meshwork. As it is well known that axons are always accompanied by glial cells, we were able to identify Schwann cells in the hilum, medullary and capsule region, like expected. Unexpected was the result, that we found oligodendrocyte-like cells in these regions, myelinating more than one axon. Likewise important was the finding, that one of the standard glial markers used, a polyclonal GFAP antibody equally bound to desmin and therefore marked nearly all stromal cells in cortical, paracortical and medullary cord regions. More detailed analysis showed that these results also appeared in many other non-lymphoid organs. Therefore, polyclonal GFAP antibodies are only conditionally usable for immunohistochemical analysis in peripheral tissues outside the central nervous system. It remains to be elucidated, if the binding of the GFAP antibody to desmin has its reason in a special desmin variant that can give stromal cells glial character.