Studies of the immune system in both clinicl and experimental burn injury have noted impairment of cellular immunity and this impaired cellular immunity after burn has been demonstrated by prolonged survival allograft, marked depression on delayed hypersensitivety or failure of lymphocyte mitogenesis. However, the exact nature of the mechanisms leading to immunosuppression remains unclear.
The aim of this study is to evaluate the level of cellular immunity in burned rats with immune paramenters of T cell subsets and colony forming unit-T lymphocyte (CFTL) as well as natural killer cell mediated cytotoxicity (NKMC).
Lymphocytes were isolated sequentially from the blood of control and experimental animals on the 1st, 3rd, 5th, 7th and 14th postburn days (PBD). T-cell subsets were defined with monoclonal anti rat T lymphocyte antibody by the indirect immunofluoroscence method. The proportions of tatal T cell (Tan T), helper T cell (Th) and helper T cel/suppressor T cell ratio decreased from the 1st PND and revealed most significant reduction on the 5th PBD (Pan T)and 7th PBD (Th, Th/Ts ratio)respectively, but they recovered by the 14th PBC.
On the contrary, the percentage of suppressor T cell (Ts) in creased after burn injury and was maximum on the 7th PBD, thereafter it decreased to the nearly control level on the 14th PBD, Number of T-lymphocyte colony (TL-colony) decreased after burn injury, and the changing pattern of its number was quite similar to that of Pan T.
The cytotoxicity of natural killer cell against Molt 4 target cells depressed rapidly after burn injury and revealed most significant reduction on the 3rd PBD, but it restored completely on the 7th PBD. Sequential change of cortisol level didn’t co-ordinate with that of cellular immunity, and it showed that stress after burn injury did not frnction as a major role to decrese cellular immunity.
The results of this study give us a speculation that immunosuppression after burn injury was resulted from decreased helper T cell, increased suppressor T cell and depressed NKMC, and that damage or recovery fo natural killer cells after burn injury is of precedence to that of the T cells.
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