ABSTRACT
In studying the immunological changes in dengue haemorrhagic fever, three phases of investigations had been carried out. During the earlier phase of investigation, significant immunological findings were obtained, namely the elevation of immunoglobulins, activation of complements, formation of circulating-immune-complexes and diminished number of T lymphocytes. The changes tended to recover during the convalescent phase. During the second phase of investigation, the extended studies revealed further confirmation of T cell impairment during the acute phase which tended to recover during the convalescent phase. Elevated number of Fc-receptor- and C3-receptor-bearing cells was also observed in some patients, variedly occurred during the acute or the convalescent phase. Elevated number of B cells was only found in small proportion. Significantly high number of activated RNA-rich lymphocytes was found in almost the half of patients. The virus-lymphocyte interaction has been demonstrated by the detection of viral antigen on the surface of lymphocytes in a proportion of patients. The circulating-immune-complexes was shown to contain viral (DEN-1) antigen. During the third phase of investigation, the impairment of T cells was further analyzed on their regulatory T populations. Impairment of total T lymphocytes, helper-T and suppressor-T was detected during the acute phase and tended to recover during the convalescent phase. The reversed changes occurred on B cells, The immunological changes and recovery are considered to be related to the stimulatory and suppressive effects of the dengue virus and regulatory mechanism.