Cellular immune response in atypical tuberculosis diagnosed by PCR in paraffin embedded material

The aim was to evaluate the cellular immune response in atypical tuberculosis and granulomatous inflammation consistent with tuberculosis (TBC), negative histochemically for acid-fast bacilli and analysed by PCR for Mycobacterium tuberculosis (MT) detection in paraffin-embedded tissue. Thirty six samples of differently localized atypical tuberculous lesions and granulomatous tuberculoid lesions negative for acid fast bacilli and 4 positive cases on Ziehl-Nielsen stain were analysed by PCR for MT detection and were tested immunohistochemically (IHC) for the cellular immune response in the granulomas and perigranulomatous tissue. The samples selected were: 7 pulmonary and 33 extrapulmonary specimens, especially lymph nodes. Histologically, the atypical tuberculous lesions contained supurative necrosis, defective granulomas and cellular polymorphism. The epithelioid cells showed frequent mitoses. The immunoprofile of cells was polymorphous. L26 positive small lymphocytes were found in nodular lymphoid aggregates surrounding granulomas. A significantly increased number of positive UCHL1 cells were found in 33 out of the 40 analysed cases, with a larger percentage of CD4 positive T cells (81.8% of cases). CD44 was positive in multinucleated giant cells (17.5% of cases), epithelioid cells (60% of cases) and lymphocytes (30% of cases). CD68 was localized in multinucleated giant cells and epithelioid cells, in a 4%, respectively 62.5% of cases. The PCR was performed in all 40 cases; the tissue samples were heterogeneous (lung, lymph nodes, lever, nasopharynx, etc.) and needed a good quality extraction of DNA. Performing a control PCR for Beta Globin tested the extraction; a good result was obtained in 31 cases (77.5%); from these, 19 cases had amplification for IS 6110. The cellular immune response in the atypical tuberculous lesions was similar in cases with and without acid-fast bacilli, but positive for PCR. In the most cases with negative PCR reaction, it was due to a deficient fixation of the material. The T lymphocytes were numerous in all types of tuberculous granulomas, with the prominence of CD4 positive subtype. The immunoprofile of the epithelioid cells, positive for CD44 and CD68, presenting frequently mitoses suggests an activate state in a possible relationship to the T-cell-mediated immune response in tuberculosis.