[Phenotypic analysis of human T-cell lymphoma with reference to cell differentiation and morphological...

The recognition of the dichotomy of the immune system was a first step in differentiating between a humoral and cellular immune response. This distinction was to be of fundamental importance in the subsequent demonstration of distinct compartments in the lymphatic cell system. Animal studies and investigations on humans with congenital immune defects soon made it possible to differentiate between functionally different cell compartments in lymphatic tissue even on morphological grounds. This formed the basis for the subdivision of lymphatic tissue into B- and T-cell areas. A multiplicity of morphologically highly varied lymphatic neoplasias confronted this clear division. In principle, there are two possible explanations for the morphological and immunological heterogeneity of neoplasias: 1. The variety of lymphatic neoplasias is an expression of a dedifferentiation of cells in which neither the morphological picture nor the immunological properties of the stem cells are expressed. 2. Lymphatic neoplasias represent stages of "arrested" differentiation in the normal cell development. The present study attempts to demonstrate the distribution and development of normal T lymphocytes by analysis of their morphology and antigen constellation. The knowledge thus gained should then make it possible to define the neoplasias of the T-cell system. Thirty-six monoclonal antibodies were employed in addition to standard enzyme-histochemical methods for demonstration of cell antigens; some of the monoclonal antibodies were developed especially for this purpose. The study included normal tissue and samples from 148 lymphomas and leukemias of the T-cell system. Subdivision of the various entities was based on morphology, which enabled us to make a direct distinction between the morphologically defined entity and its corresponding phenotype. These phenotypic analyses of malignant T-cell lymphomas were conducted in pursuit of 3 basic goals: 1. To catch T-cell neoplasias in the full variety of their phenotypical spectrum by using assorted T-cell properties. 2. To bring these varied entities into a sequence corresponding to normal cell differentiation by correlating the neoplasias to normal cell compartments. 3. To determine the extent to which neoplastic equivalents exist for normal T cells with varied phenotypes and/or functional properties. A clear morphological subdivision of the T-cell neoplasias is already possible: 1. lymphoblastic lymphomas and leukemias; 2. peripheral or mature cell T-cell lymphomas. The lymphoblastic lymphomas and leukemias have until now been characterized primarily according to their positivity for the enzyme TdT. The T-lymphoblastic lymphomas and leukemias we analysed phenotypically shared the constant features of CD7 antigen expression, whereas other T-cell features showed a clear variability.