Generation of in vitro natural cytotoxicity of horse lymphocytes against sarcoid-derived tumor cells not expressing major histocompatibility complex antigens.
OBJECTIVE
To analyze in vitro lymphocyte-mediated immune responses of horses with sarcoids against allogeneic sarcoid cells containing endogenous retrovirus but not expressing major histocompatibility complex antigens.


METHODS
Lymphocyte-mediated immune reactions were assessed by means of proliferative responses in mixed lymphocyte tumor cell culture (MLTC) assay and lymphocyte-mediated cytotoxicity against various equine target cells.


METHODS
12 horses with sarcoid tumors and 15 control horses.


METHODS
Blood lymphocytes were cocultured in MLTC with allogeneic sarcoid cells (Mc-1, BayMc-1), equine testis cells, or normal equine dermal fibroblasts. Lymphocytes were assayed for proliferative responses by [3H]thymidine uptake and for cytotoxicity against the same targets by 51Cr release assay. The lymphocyte populations were analyzed for some common surface markers.


RESULTS
Lymphocytes from horses with sarcoids exerted an anamnestic proliferative response in MLTC against Mc-1 cells, but this procedure never generated cytotoxic lymphocytes. However, lymphocytes from all horses cultured in medium with 10% allogeneic serum only had selective. natural cytotoxicity against Mc-1 that was generated without DNA synthesis. Approximately 80% of the lymphocytes disappeared during culture; however the remaining population of small, viable lymphocytes indicated a decrease of CD4+ T lymphocytes, but numbers of T cells with receptors for Helix pomatia A hemagglutinin were unaffected. Few lymphocytes had Fc-receptors for IgG, were complement-reactive positive cells or were B cells expressing surface immunoglobulin.


CONCLUSIONS
Results may indicate a natural defense system, which preferentially recognizes and lyses tumor cells that are deficient in surface expression of major histocompatibility complex antigens, without intervention of conventional T-cell receptors or antibodies.
Broström
H
H
Department of Medicine and Surgery, Swedish University of Agricultural Sciences, Uppsala, Sweden.
Troye-Bomberg
M
M
Perlmann
P
P
D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D002478:Cells, Cultured; D003602:Cytotoxicity, Immunologic; D015395:Histocompatibility Antigens Class I / Q000032:analysis; D000949:Histocompatibility Antigens Class II / Q000032:analysis; D006734:Horse Diseases; D006736:Horses / Q000276:immunology*; D008213:Lymphocyte Activation; D008285:Major Histocompatibility Complex; D012016:Reference Values; D012509:Sarcoma / Q000276:immunology / Q000662:veterinary*; D012867:Skin / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology*
D015395:Histocompatibility Antigens Class I; D000949:Histocompatibility Antigens Class II