Search

A monoclonal antibody OKT 9 which detects a determinant expressed by a variety of proliferating cell types has been recently developed. This antibody was used in conjunction with the immunoperoxidase technique to study the cutaneous lymphoid infiltrates of nine patients with mycosis fungoides, one patient with lymphomatoid papulosis, two patients with Sézary syndrome, and ten patients with large plaque atrophic parapsoriasis (a condition which may terminate in overt mycosis fungoides.) OKT 9 reactive cells were identified in all cases of mycosis fungoides examined, in one case of lymphomatoid papulosis, one of two cases of Sézary syndrome, and one of ten cases of large plaque atrophic parapsoriasis. These results suggest that further studies using OKT 9 should be performed to assess whether OKT 9 reactivity may be used as a prognostic marker in cutaneous lymphomas and prelymphomas.

Human thymocytes at an intermediate stage of differentiation were demonstrated in situ in tissue sections of thymus using the mouse monoclonal antibody OKT 6 THY (Ortho Immunobiology Ltd, Raritan, NJ) and the immunoperoxidase technique. These cells were found to reside mainly within the thymic cortex. The effects of on-slide fixation on the ease of demonstration of the antigen involved were assessed. The choice of fixative was found to have a marked effect, acetone and paraformaldehyde producing the most satisfactory results.

A monoclonal antibody (OKT10), which was developed recently, reacts with pro-thymocytes, T cell acute lymphoblastic leukemia (ALL) cells, cells in normal bone marrow (including plasma cells), and activated T cells. Tissues from patients with cutaneous T cell lymphoma were studied for the presence of OKT10-reactive cells with the use of an indirect immunoperoxidase technic. OKT10-reactive cells were identified in three of eight cases of mycosis fungoides, one of two cases of Sézary syndrome, with an equivocal reaction in one of ten cases of large-plaque parapsoriasis and in one of seven positive patch tests (allergic contact dermatitis). The biologic and possible clinical implications are discussed.

Surface markers expressed on histiocytosis X (HX) cells were studied using 18 monoclonal antibodies (McAbs) and an in situ indirect immunoperoxidase technique. Specimens of skin (five biopsies from three cases) and lymph node (one case) were studied. Our study confirmed previous findings of an OKT6+ HLA DR+ Leu 3a+ phenotype of HX cells in skin and indicated that lymph node HX cells can also have this phenotype. A mixture of cells expressing T markers/T subset, monocyte/macrophage, and killer/natural killer (K/NK) markers was also present in two cases. However, one case with an aggressive course showed no detectable HNK 1+ (K/NK) or Leu 2A (suppressor) cells in the cutaneous infiltrates and no detectable HNK 1+ lymphocytes in an affected lymph node. The significance of these findings in relation to prognosis and therapy is discussed.

In situ immunologic phenotyping of the cutaneous lymphoid infiltrates of five cases of mycosis fungoides (MF) was performed. This was done by the immunoperoxidase technic using monoclonal antibodies directed against normally expressed by mature peripheral T cells and T cells subsets. A significant proportion of the infiltrates reacted with peripheral T cell antibodies. In addition, "helper" predominance was demonstrated. However, cells reacting positively with "suppressor" antibodies were also demonstrated in three cases, indicating immunologic heterogeneity of the infiltrates. The presence of a significant component of the infiltrates yielding an equivocal or negative reaction with the mature T cell antibodies, especially in the infiltrates of one case which had a fatal outcome, suggests further heterogeneity with the presence of immature cells. Future investigation with monoclonal antibodies directed against immature T cell differentiation antigens will be of interest.

A study was performed using monoclonal antibodies and the immunoperoxidase technic to identify T-cells and T-subsets in human tonsil sections. The in situ topographic identification of T-cells, helper cells, and suppressor cells was achieved. This model may therefore be applied to other normal lymphoid tissues. Its potential pathologic importance lies in the fact that certain disorders may be associated with depletion of lymphocyte subsets from their normal areas of "homing," and that lymphoma cells may mirror their putative normal counterparts in their selective metastatic migration pattern. The improved knowledge of normal lymphocyte subset microenvironment afforded by this technic may therefore be of value in applied pathology.

Infiltrates of five cases of mycosis fungoides (MF) were studied for the presence of cells reactive with a monoclonal antibody, OKT 6, which detects an antigen present on relatively immature thymocytes and Langerhans cells. In situ immunohistochemical staining was used for their demonstration. OKT 6-reactive cells formed a definite component of the dermal infiltrates of all patients examined. In three patients who showed numerous Pautrier microabscesses on routine histologic examination, OKT 6-positive cells were found to form a component of these abscesses. OKT 6-reactive cells have also recently been shown to be present in varying numbers in the dermal infiltrates of large plaque (atrophic) parapsoriasis (LPAP), a condition which may terminate in MF. The significance of these findings is discussed.

The T cell nature of mycosis fungoides and Sézary syndrome was established a decade ago. The recent advent of monoclonal antibodies to T cells and other lymphoid subpopulations has resulted in an explosion of knowledge on the biology of this group of disorders. These reagents have increased our knowledge on thymic differentiation status, pathogenesis, the phenotype of premalignant vs malignant lymphocytic infiltrates, the identification of other previously unrecognized cells within lymphomas, and the phenotype of circulating vs skin lymphocytes. Therapeutic applications may result. These new developments are discussed.

This report describes the in situ demonstration of "T" lymphocytes and "T" lymphocyte subsets in tissue sections using a case of lichen planus as a model. The technique utilized is the indirect immunoperoxidase method with monoclonal antibodies to "T" cells and "T" cell subsets. In the case examined a predominance of helper "T" cells was found. The potential application of this method in the immunopathology of skin and internal organs is discussed.

The development of monoclonal antibodies to T cells at various stages of differentiation, B cells and histiocytes, suggests that these reagents may be of use in the diagnosis and categorization of cutaneous lymphomas. The findings to date in skin and blood are discussed.

An immunoperoxidase study was carried out on human tonsil (15 specimens) and human lymph node (5 specimens) using OKT6, a monoclonal antibody which was raised against a determinant on immature thymocytes. OKT6-positive cells were identified in the crypt epithelium of all tonsils examined and in occasional clusters in the interfollicular areas of two lymph nodes. OKT6 has recently been shown to react with epidermal dendritic cells (Langerhans' cells). This study confirms that OKT6-reactive cells may be found outside the thymus. The pattern of staining obtained suggests that OKT6 reactivity belongs to a dendritic subpopulation. The significance of the finding in relation to physiology and pathology is discussed. These physiological findings may also be relevant to the immunotherapy of T-cell lymphomas.