Effect of hydrocortisone on the in vitro human antibody response: interaction with monocytes and prostaglandins

Glucocorticoid effects on natural and humoral immunity in mallards

Two studies were conducted to determine the effects of dexamethasone (DEX) on immune function in mallard ducks. Each day ducks were injected intramuscularly with DEX at doses ranging from 0.2-4.0 mg/kg for 28-30 days. Physiologic effects consistent with high dose glucocorticoid (GC) treatment were observed at the 4 mg/kg dose, and included significant body weight loss, lowered hematocrit, and elevated alanine aminotransferase (ALT) activity. At all doses, effects of DEX on the immune system were observed. When DEX was given at 0.2 mg/kg/day, significant suppression of primary IgG antibody titers to sheep erythrocytes (SRBC) was observed. At 1 mg/kg/day, primary IgM and secondary IgM and IgG titers were suppressed as well. These doses of DEX also produced significant elevation in natural killer cell (NKC) activity of peripheral blood mononuclear cells (PBMNC). Removal of adherent cells from the PBMNC prior to NKC assay eliminated the enhancement in NKC activity. Based on these results, it was postulated that the elevation in NKC activity may be due to suppression by DEX of monocyte production of prostaglandin-E2 (PGE-2) resulting in the release of NKC activity from the inhibitory effects of PGE-2. This hypothesis was supported by a measured decrease in PGE-2 production during the NKC assay by cells from DEX-treated birds. Furthermore, an enhanced NKC activity could be reproduced in vitro with the addition of indomethacin or DEX to NKC cultures containing adherent cells from PBMNC. Direct effects of DEX on nonadherent cell NKC activity and lymphocyte viability were only observed at high concentrations (10(-4) M) of DEX, while the phagocytic activity of adhered blood monocytes was inhibited at 10(-6) M DEX. The suppressed phagocytic activity may contribute to the suppressed antibody responses observed in DEX-treated birds. Together, these results support an indirect immunomodulatory effect of DEX on NKC activity and perhaps antibody responses in vivo via altered monocyte function in mallard ducks.

The role of prostaglandin E2 in immune suppression following injury

It has been thought for some time that prostaglandin E2 (PGE2) released from activated monocytes/macrophages may contribute to the suppression of immunity seen after burns and major injury because PGE2 inhibits the activation of T lymphocytes. To clarify this issue, we studied 15 patients with total body surface area burns of 20% to 90% (mean, 48%). Peripheral blood mononuclear cells (PBMC) were obtained from these patients one to two times each week for 1 month after burn and were stimulated with the T-cell mitogen phytohemagglutinin (PHA). On 14 occasions the PBMCs from eight patients were significantly suppressed (30% or more) in their response to PHA (suppressed [sup] burn) as compared with PBMCs from normal controls. In 38 instances PBMCs from 12 patients were not significantly suppressed in PHA (nonsuppressed [nonsup] burn). Sup burn PBMCs and control PBMCs were cultured with or without the addition of the cyclooxygenase (CO) inhibitor indomethacin (Indo, 1 microgram/mL) and studied for PHA response and the production of the stimulatory cytokine interleukin-2 (IL-2). Indo partially restored the PHA response of sup burn PBMCs to normal. Sup burn PBMCs also were deficient in production of IL-2. Indo increased IL-2 production by sup burn PBMCs significantly more (160% +/- 20%, p less than 0.005) than control (57% +/- 5%) and nonsup PBMCs (67% +/- 8%). Next inhibition of the PHA response of PBMCs from 12 burn patients and 17 controls was studied by exogenous PGE2. At all time periods after burn injury, patients' PBMCs were significantly more sensitive to inhibition by PGE2 (50% inhibition at 10(-8) mol/L [molar] PGE2) than PBMCs from normal controls (50% inhibition at 10(-6) mol/L PGE2) with maximum sensitivity occurring 8 to 14 days after injury. Peripheral blood mononuclear cells from patients with more than 40% burns were significantly (p less than 0.05) more sensitive to PGE2 than those from patients with lesser burns. Interleukin-2 was added to cultures of sup burn PBMC, nonsup burn PBMC, and controls containing 10(-7) mol/L PGE2. Interleukin-2 totally reversed PGE2 inhibition of the PHA response in PBMC from both controls and burn patients. Because endotoxin leak from the gut has been implicated as a trigger for a number of the metabolic and immunologic abnormalities following injury, the authors looked for the effect of a bolus infusion of Escherichia coli endotoxin (Endo, 4 ng/kg) in seven normal healthy volunteers on the response of PBMC to PHA and on the production of PGE2 and IL-2.(ABSTRACT TRUNCATED AT 400 WORDS)

Cystic fibrosis patients' B-lymphocyte response is resistant to the in vitro enhancing effect of corticosteroids

Cystic fibrosis is associated with an cAMP-regulated channel defect, which has been evidenced in many cell types including B lymphocytes. To document a B-cell dysfunction potentially related to this defect, we studied the in vitro IgG production by lymphocytes from 11 cystic fibrosis patients. B lymphocytes were co-cultured with autologous monocytes and stimulated with Staphylococcus aureus Cowan or with Nocardia-delipidated cell mitogen in the presence of low concentrations of IL2. Cystic fibrosis patients' cells produced amounts of IgG comparable with that of normal and control patients' cells. However, dexamethasone (10(-7) mol l-1) had no effect on the response of cystic fibrosis patients' cells, whereas it enhanced that of the latter two groups. This resistance of cystic fibrosis cells was true with concentrations of dexamethasone up to 10(-6) mol l-1, whereas this agent induced a dose-related enhancement from 10(-8) to 10(-6) mol l-1 in cultures of normal cells. Co-culture experiments showed that cystic fibrosis B lymphocytes themselves are resistant to the effect of dexamethasone. In contrast dexamethasone normally suppressed the anti-CD3 antibody-induced response of cystic fibrosis T cells in the presence of IL2 and the IL1 alpha- or beta-induced collagenase production of cystic fibrosis fibroblast cell lines. Thus cystic fibrosis B lymphocytes exhibit a selective defect which may interfere with the normal interactions between the hormonal and immune systems and may participate in the sensitivity of cystic fibrosis patients to bacterial bronchopulmonary infections.

A study on plasma prostaglandin E2 levels in hepatitis B carriers and patients with chronic active hepatitis

Prostaglandin E2 (PGE2), one of the major prostaglandins synthesized in human monocyte and macrophage, is able to modulate T lymphocyte reactivity, such as lymphokine secretion and cytotoxicity. Some immunologic abnormalities such as alteration in the synthesis of PGE2 by monocyte and macrophage or in the response of T lymphocytes to PGE2 can be found in clinical disease.

We measured the plasma PGE2 level in the control group and patients with chronic liver disease.

The results were obtained as follows. The mean plasma PGE2 level was 2.65 ± 0.69 pg/ml in the control group. The mean plasma PGE2 level was 9.07 ± 5.89 pg/ml in 15 patients with chronic active hepatitis and was significantly higher than that of the control group (p<0.01). The plasma mean PGE2 level was 4.65 ± 1.59 pg/ml in 8 patients in the healing stage or stable stage of chronic hepatitis and was tend to decrease. However, this decrease is significantly different from that of the control group. The plasma PGE2 level was 3.5 ± 0.92 pg/ml in 4 hepatitis B carriers and was not significantly different from that of the control group (p<0.05).

This results suggest that plasma PGE2 can be used for the measurement of cell-mediated immunity and follow-up study in patients with chronic active hepatitis and hepatitis B carriers.

Hypogammaglobulinaemia associated with long term, low dose steroid therapy

Repeated pneumonia and hypogammaglobulinaemia was associated with long term low dose steroid therapy. Clinical improvement with restoration of antibody levels followed substitution of aerosol for oral therapy.

Detection of anti-HBc IgM following prednisone treatment in patients with chronic active hepatitis B virus infection

The effect of a short course of prednisone therapy on serum IgM type antibody to the hepatitis B core antigen (anti-HBc IgM) was studied in 14 male patients with chronic active type B hepatitis. Eleven patients (78.5%) became positive for serum anti-HBc IgM either during or shortly after prednisone withdrawal. Detection of anti-HBc IgM correlated with an increase in hepatitis B virus specific DNA-polymerase activity and was followed by a rise in serum transaminase levels. Six patients with histologic evidence of cirrhosis developed anti-HBc IgM which lasted six or more months after prednisone therapy and had a rapid onset of hepatic decompensation manifested by encephalopathy with ascites and/or variceal bleeding. In 17 untreated chronic active type B hepatitis patients who served as controls, anti-HBc IgM was detected at low levels in only a single serum sample from each of two patients during the same observation period.

Prostaglandin E2 regulation of human specific B-cell response: interaction with a monocyte product

The effect of exogeneous prostaglandin E2 (PGE2) on the specific plaque-forming cell (PFC) response in cultures of non-adherent human peripheral blood mononuclear cells (PBM) was tested. When added on Day 2 of the cultures PGE2 inhibits the induction of the PFC response, and the maximum inhibition (50%) is obtained with 300 nM PGE2. When PBM are cultured during the first 24 hr with the same concentration of PGE2 their PFC response is enhanced and the target of this enhancement is a T cell. When PGE2 is added on Day 0 it does not affect the response, probably because of a balance between these two opposing effects. However, in the latter conditions a prostaglandin-free monocyte supernatant can render PGE2 suppressive. The monocyte supernatant acts by inhibiting the stimulatory effect after the interaction between PGE2 and T cells. Thus the effect of PGE2 depends on its time of action and on the concomitant production of a nondialyzable factor by monocytes.