Immunohistochemical characterisation of the lymph node reaction in pig post-weaning multisystemic wasting syndrome (PMWS)

The superficial inguinal lymph nodes of 10 piglets which had died spontaneo usly of postweaning multisystemic wasting syndrome (PMWS), in which the por cine circovirus type II (PCV-II) genome was revealed by PCR, were submitted to immunohistochemical investigation for CD4, CD8, IgM, MAC387, S-100 prot ein, vimentin and F-VIII-RA and compared with three normal cases. The lymph node reaction was graded as initial, intermediate and end stage according to histological criteria. In the initial and intermediate stages, absence o f follicles and depletion of lymphocytes were evident. Associated with this was a reduction in numbers of interfollicular dendritic cells and interdig itating cells and a reduction/absence of B cells and mainly CD4+ T lymphocy tes. In the end stage the reduced expression of high endothelial venules an d the prevalence of the stromal component of the lymph node was prominent, as well as the above changes. It is concluded that more than one mechanism is involved in the immunosuppressive ability of PCV-II: reduction of the an tigen presenting ability and reduction of B cells and CD4+ T cell function. (C) 2001 Elsevier Science B.V. All rights reserved.