The effects of immunosuppressive treatment on natural-killer-cell activity and the manifestation of
eperythrozoonosis in swine were investigated. After
infection with Eperythrozoon suis (E. suis), German Landrace piglets received daily intravenous (i.v.) applications of
cyclophosphamide (CY,
Endoxan) on 6 consecutive days. A combined immunosuppressive treatment using
azathioprine (Imurek), a single application of
dexamethasone (Devan), and two
injections of anti-
asialo GM1 serum (1:50) was performed with a piglet over a period of 9 days. Leucocyte counts, differential blood-cell count, and microhaematocrit and rectal temperature were controlled. Direct microscopic observation of E. suis organisms was performed in Giemsastained blood smears. Immunosuppressive treatment resulted in relative
lymphocytosis and transient
agranulocytosis. CY and
azathioprine therapy caused a temporary increase of E. suis organisms in red blood cells. Natural-killer-(NK) cell activity mediated by
nylon-wool non-adherent peripheral-blood mononuclear leucocytes (
NAD-PBML) was recorded during and after immunosuppressive treatment of pigs infected with E. suis. Cytotoxic activity of NK cells was consistently reduced after two CY
injections and further decreased to 70-100% of the initial NK-mediated
tumor cell lysis.
NAD-PBML of two E. suis infected animals were monitored for cytotoxicity during CY immunosuppressive treatment and were compared to
Percoll density separated NK effector cells derived from the same blood sample. Enhancement of NK-cell activity by density separation of
NAD-PBML was not longer possible on days 3 and 4 during CY treatment, indicating a decrease of NK cells in peripheral blood. In vitro, only a high dose of CY (4 microgram/ml) suppressed cytolytic activity of
NAD-PBML. Short-term treatment with
immunosuppressive agents did not replace
splenectomy in inducing clinically apparent
eperythrozoonosis.