A freeze-dried paraffin-embedded tissue technique for immunohistochemical studies requiring unfixed tissue from the nervous system.

Immunohistochemical studies using monoclonal antibodies against epitopes in neural tissues frequently require tissue which has not been fixed in formalin. In the past, such studies have been performed on frozen (cryostat) sections despite the general loss of morphological preservation compared with paraffin sections. In the present report, a detailed, versatile method for obtaining improved morphological preservation of "unfixed" neural tissue is described which utilizes freeze-dried paraffin-embedded sections (a modified Altmann-Gersh technique). The advantages of using mercury flotation of freeze-dried sections are particularly stressed.