Feng-Yee Chang

Decreased cell-mediated immunity in patients with non-insulin-dependent diabetes mellitus.

Peripheral blood mononuclear cells from patients with non-insulin-dependent diabetes mellitus (NIDDM) show reduced proliferative response to phytohemagglutinin (PHA) and other mitogens. This study was undertaken to determine whether this reduced lymphocyte proliferation is mediated by a decreased production of cytokine or decreased expression of interleukin-2 receptor (IL-2R). Mononuclear cells from NIDDM patients (n = 34) and healthy controls (n = 22) were cultured in RPMI-1640 media containing PHA, concanavalin-A and phorbol myristate acetate. NIDDM patients showed reduced [3H]thymidine uptake (57% of controls, P < 0.01), reduced percentage of IL-2R-positive cells (61% of controls, P < 0.02) and increased level of tumor necrosis factor (TNF)-alpha (200% of controls, P < 0.05). The percentage of complement receptor (CR) 3-positive monocytes from NIDDM patients was also decreased (72% of controls, P < 0.05). However, the production of IL-1 beta, IL-2 and interferon-gamma, the percentages of pan T cells (CD3), T helper cells (CD4), T suppressor cells (CD8), the ratio of CD4/CD8 and the expression of CR1 and Fc receptors for immunoglobulin G (Fc gamma RII and Fc gamma RIII) were not significantly different between NIDDM patients and healthy subjects. Human recombinant IL-2 was unable to restore the [3H]thymidine uptake by PHA-stimulated mononuclear cells from NIDDM patients. Elevation of glucose concentration up to 27.8 mmol/l in the culture medium did not suppress the [3H]thymidine uptake and IL-2R expression by activated lymphocytes from healthy subjects. The decreased expression of IL-2R on activated lymphocytes might be responsible for the insufficient lymphocyte proliferation in NIDDM patients. These findings suggest that decreased expression of CR3 on monocytes, decreased lymphocyte proliferation and decreased IL-2R expression despite a higher production of TNF-alpha may explain the impaired cell-mediated immunity seen in NIDDM patients.

Respiratory burst activity of monocytes from patients with non-insulin-dependent diabetes mellitus

Monocytes from patients with poorly controlled non-insulin-dependent diabetes mellitus (NIDDM) show a decrease in intracellular bactericidal function. To determine whether this reduced bactericidal function is mediated by an impaired oxygen-dependent mechanism, we assayed the production of superoxide (O2-) and hydrogen peroxide (H2O2) by monocytes from poorly controlled NIDDM patients (n = 12), well controlled NIDDM patients (n = 12) and healthy subjects (n = 16). Using phorbol myristate acetate (PMA) as stimulant, the production of O2- by fresh monocytes was significantly decreased in poorly controlled NIDDM patients (231 +/- 30 nmol/mg protein/2-h) as compared with that of well controlled NIDDM patients (430 +/- 81 nmol/mg protein/2-h) and that of healthy subjects (399 +/- 61 nmol/mg protein/2-h), respectively (P < 0.05). Using opsonized zymosan (OZ) as stimulant, the production of O2- by fresh monocytes was also notably decreased in patients with poorly controlled NIDDM (312 +/- 42 nmol/mg protein/2-h) as compared with that of patients with well controlled NIDDM (688 +/- 92 nmol/mg protein/2-h) and that of healthy subjects (539 +/- 96 nmol/mg protein/2-h), respectively (P < 0.05). Poorly controlled NIDDM patients had a significant decrease in the production of H2O2 by monocytes, either stimulated by PMA or OZ, as compared with that of well controlled NIDDM patients and that of healthy subjects, respectively (P < 0.05). Enhancement of the production of O2- and H2O2 occurred in healthy subjects (150% increase) as well as NIDDM patients (170% increase) after a preincubation of monocytes with interferon-gamma (IFN-gamma 100 U/ml) for 48 h. The respiratory burst activity of both fresh and cultured monocytes from well controlled NIDDM patients was not significantly different from that of healthy subjects. This study suggests that both, strict metabolic control and in vitro culture with IFN-gamma may improve the monocyte oxygen-dependent bactericidal mechanism in NIDDM patients.

Complement pathway activity in serum from patients with classical dengue fever

Complement activity in 125 cases of classical dengue fever was examined through the measurement of haemolytic activity. During the first 3 d of fever, the classical complement pathway activity (CCPA) was not altered in 109 cases. After 4 d of fever, 9 of 16 patients in the viraemic period had CCPA decreased by 45% (995 +/- 119 units/ml) and serum complement component C4 decreased by 40% (10.4 +/- 0.9 mg/dl). The alternative complement pathway activity was not affected in any case tested throughout both viraemic and convalescent stages. Both CCPA and C4 persistently decreased in 3 of these 9 patients at the convalescent stage. A decrease in serum C3 was also observed in these 3 patients only, and circulating immune complexes (CIC) levels were particularly high in these 3 patients. These results indicate that there is little evidence of complement activation on days 1-3 of viraemia but that complement activation may occur subsequently. It is concluded that both CIC and other unknown factors not related to CIC may contribute to complement activation in some cases (9/125) of classical dengue fever.

The role of immunoglobulin and complement in enhancing the respiratory burst of neutrophils against Trichomonas vaginalis

Summary Human neutrophils. alone, did not kill Trichomonas vaginalis. More than 90% of T. vaginalis (105/ml) survived in the presence of 10% normal human serum (NHS) while 90% of these organisms were killed in the presence of a combination of neutrophils (106/ml) and 10% NHS. Mechanisms responsible for this serum‐mediated neutrophil killing of T. vaginalis were demonstrated through a process of lucigenin‐amplified neutrophil chemiluminescence. As evidenced by indirect immunonuores‐cence, NHS showed specific immunoglobulin G (IgG) titre of 1:8 for T. vaginalis. Purified IgG, at 1.6 mg/ml, showed no direct opsonizing or lytic effect on ibis organism. Formalin‐fixed trichomonads opsonized by C2 deficient human serum promote 4 times more neutrophil chemiluminescence than those opsonized by Factor B deficient human serum. With the addition of purified IgG (5 mg/ml) neutrophil chemiluminescence was increased by 4 times and further improved trichomonal killing by neutrophils (from 5 ± 4% to 78 ± 16%) via activation of the classical complement pathway, but did not alter that due to activation of the alternative complement pathway. These studies indicate that both an IgG‐enhanced classical complement pathway activation and an antibody‐independent alternative complement pathway activation provide opsonin (C3) for T. vaginalis to facilitate the neutrophil killing mechanism.

In vitro Effect of Actinomycin D on Human Neutrophil Function

The effect of actinomycin D (ACT‐D) on human neutrophil chemotaxis, chemiluminescence (CL), superoxide (O2‐) production, phagocytic uptake, and intracellular bacterial killing has been examined. The viability of the ACT‐D‐treated neutrophils was 9800 even at a concentration of 10 μg/ml for 4 hr. Using fMLP as the chemotactic factor, depressed chemotaxis was demonstrated following ACT‐D (1 10 μg/ml) pretreatment of neutrophils as compared with the non‐treated controls. Similar ACT‐D pretreatment produced the depressed responses in phorbol myristate acetate‐induced CL and superoxide production by neutrophils. Moreover, using heat‐inactivated human serum as an opsonin for Salmonella enteritidis (NCTC 6676), there was a significant difference in intracellular killing (P<0.01) but no difference in phagocytic uptake between ACT‐D‐treated and non‐treated neutrophils. These studies indicate that ACT‐D profoundly impairs both intracellular bacterial killing by human neutrophil through an effect on respiratory burst activity and directed cell migration of human neutrophils.

Pentoxifylline Pretreatment Enhances the Oxidative Burst Activity of Human Peripheral Blood Mononuclear Cells

The effect of pentoxifylline pretreatment on the lucigenin‐augmented chemiluminescence and dismutase‐inhibitable superoxide production of human neutrophils and mononuclear cells (MNCs) was studied. Pentoxifylline at 20–2,000 μg/ml enhanced the lucigenin‐augmented chemiluminescence (118–165% of the control, P < 0.01) of phorbol myristate acetate (PMA)‐stimulated MNC. Pentoxifylline at 20–2,000 μg/ml increased the MNC superoxide production, i.e., 142–171% of the control (P < 0.05) using PMA stimulation and 145–159% of the control (P < 0.01) using opsonized zymosan stimulation. In contrast, pentoxifylline (up to 2,000 μg/ml) did not influence the lucigenin‐augmented chemiluminescence and superoxide production of human neutrophils, stimulated by either PMA or opsonized zymosan. These results suggest that pentoxifylline is an immunomodulator and may have potential usefulness in the enhancement of immune defenses in compromised hosts.