Immunoglobulin (IgG and IgM) metabolism in patients with rheumatoid arthritis

Distribution of immunoglobulin-containing cells in human bone marrow and lymphoid tissues

Cell suspensions of human bone marrow, spleen, lymph nodes and palatine tonsils have been investigated for the presence of intracellular immunoglobulins by a direct immunofluorescence technique, using monospecific antisera against human Ig heavy chains alpha, mu and gamma and light chains kappa and lambda. Serum Ig levels were determined and the number of positive cells was compared with the concentration and calculated synthetic rate of serum Ig in each individual. The 28 patients studied covered a wide range of diagnoses and included those with normal as well as pathologically decreased or increased serum Ig levels. There was a high correlation between the calculated synthetic rate of each Ig class and the percentage of cells positive for the same Ig class in the bone marrow but not in the spleen, lymph nodes or tonsils. The Ig-containing cells constituted a much larger proportion of the total lymphoid cell population in the bone marrow than in the peripheral lymphoid organs. The estimated total number of Ig-containing cells was also much larger in the bone marrow than in the other organs investigated. It is concluded that in man the bone marrow is the major site of serum Ig synthesis and that the average synthetic rate per cell is the same regardless which of the three major Ig classes is produced. The role played by different lymphoid organs in humoral immunity is discussed in the light of the present results and reported data regarding lymphocyte and plasma cell kinetics in mammals.

Filtration as the main transport mechanism of protein exchange between plasma and the peritoneal cavity in hepatic cirrhosis

Fractional peritoneal reabsorption rates (FPRR) were determined from the plasma activity after simultaneous intraperitoneal injection of 131I-labelled serum albumin (a) and 125I-labelled immunoglobulin G-IgG (g) in eight patients with cirrhosis (+ ascites 6, -ascites 2) and in one patient with carcinomatous ascites. Trans-vascular escape rates of albumin (TERa) and IgG (TERg) were determined in the cirrhotic patients from the disappearance of simultaneously intravenously injected 131I-labelled serum albumin and 124I-labelled IgG. Peritoneal space to plasma appearance times ranged 0.1-3.3 h, and the appearance times of albumin and IgG were almost identical. In patients with cirrhosis FPRRa and FPRRg were on average 1.27 and 1.21% of intraperitoneal protein masses returning to plasma per hour, respectively. Mean FPRRg/FPRRa ratio was 0.95 and this value was not significantly different from unity, but significantly higher (P < 0.001) than the ratio between the free diffusion coefficients of IgG and albumin (0.06). The calculated ascitic fluid flow rate was on average 61 ml/h. TERa and TERg were on average 9.6 and 8.6% of intravascular protein masses per hour, mean TERg/TERa ratio was 0.95. Peritoneal space to plasma protein flux averaged 0.4% of the intravascular protein mass per hour. The results point to filtration (convective flux) as the main transport mechanism responsible for protein passage into the peritoneal cavity as well as for the protein passage (lymphatic drainage) back into the plasma. Pressure measurements during catheterization confirmed pressure differences essential for convective flux.

Filtration as the main mechanism of increased protein extravasation in liver cirrhosis

Transvascular escape rates of albumin and immunoglobulin-G, IgG (TERalb and TERIgG, i.e, the fractions of intravascular mass of albumin and IgG passing to the extravascular space per unit time) were determined simultaneously from the disappearance of intravenously injected 131I-labelled human serum albumin and 125I-labelled human IgG in eight patients with cirrhosis of the liver. The mean wedged hepatic venous pressure was 22 mmHg (range 13-34). TERalb and and TERIgG/TERalb ratio was on average 8.4 +/- 0.8%/h (SD), and 7.4 +/- 1.9%/h (SD), respectively and these values are significantly increased compared to normal subjects [TERalb = 5.2 +/- 1.0 %/h (SD) and TERIgG = 3.0 +/- 0.7 %/h (SD), P less than 0.001]. The TERIgG/TERalb ratio was on average 0.88 +/- 0.20 (SD), which is significantly higher than that of normals [0.58 +/- 0.08 (SD), P less than 0.005]. The results indicated that increased filtration (bulk flow) is the dominant process of the increase microvascular protein escape in cirrhosis, due most likely to increased hepatic, but also to increased extrahepatic splanchnic transcapillary protein flux.

Metabolism of autologous and homologous IgG in rheumatoid arthritis

The metabolism of radioiodinated IgG was studied in 20 patients with rheumatoid arthritis and 11 normal controls using autologous IgG and homologous IgG pooled from normal donors. Fractional catabolic rates in the controls were 4.44% of the autologous- and 4.29% of the homologous-labeled protein per day. The corresponding rates in the rheumatoid patients were 9.67% of the autologous- and 8.64% of the homologous-labeled protein per day. Extravascular catabolism occurred only in the rheumatoid group and accounted essentially for the entire increased catabolism of IgG observed in these patients. 10 patients were especially hypercatabolic, with fractional catabolic rates for autologous IgG greater than 10%. Moreover, they catabolized their autologous IgG significantly faster than the homologous IgG (12.6 vs. 9.9%). The increment of catabolism of autologous over homologous IgG also occurred in the extravascular compartment. These highly hypercatabolic patients had a significantly increased number of manifestations of extra-articular disease. The hypercatabolism of IgG could not be correlated with age, weight, sex, duration of disease, joint erosions, corticosteroid therapy, erythrocyte sedimentation rate, rheumatoid factor titer, serum IgG concentration, or circulating immune complexes as measured by the Raji cell radioimmunoassay. Conceivable sites of extravascular catabolism and possible causes of faster catabolism of autologous (rheumatoid) than of homologous (normal) IgG are discussed.

Increased transcapillary escape rate of albumin and IgG in essential hypertension

Transcapillary escape rates of albumin and IgG (fractions of intravascular mass of albumin and IgG that pass to the extravascular space per unit time) were determined simultaneously from the initial disappearance of intravenously injected 131I human albumin and 125I human IgG in seven untreated subjects suffering from essential hypertension. The average mean arterial blood pressure of these subjects 193/119 mmHg; four subjects had grade I-III funduscopic changes. Transcapillary escape rates of albumin (TERalb) and IgG (TERIgG) were found significantly increased in the hypertensive subjects, average 7.8 +/- 0.9 (SD) and 4.7 +/- 1.0 (SD) %/h, respectively, compared with normal values of mean 5.2 +/- 1.0 (SD) and 3.0 +/- 0.7 (SD) %/h, respectively (P less than 0.01). There was a statistically significant positive correlation between the mean arterial blood pressure and TER of albumin and of IgG (P less than 0.001). The TERIgG/TERalb ratio was about the same in the hypertensives and the normals. Confirming a previous observation, we found an increase in the daily urinary albumin excretion rate from a normal average of 9.1 (range, 2.4-20.4)mg/24 h to 96 (range, 5.6-565) mg/24 h, P less than 0.05. The present findings can best be explained by increased filtration through normal pores between the endothelial cells in the microvasculature, due to the high arterial blood pressure.

Clinical and biochemical assessment of anti-inflammatory substances

To assess the efficiency of anti-inflammatory drugs in human beings one has first to choose between acute and chronic inflammatory diseases and the length of the trial according to their pharmacological properties determined in animal. Further clinical criteria of efficiency will be selected on the basis of their measurable and objective characteristics. Biological criteria becomes more and more useful to judge efficiency of the drugs which possess no or very little effect on acute phase of inflammation: inflammatory blood tests, urinary excretion of hydroxyproline and immunological analysis such as quantitative determinations of immuno-globulins and rheumatoid factors and lymphocytic functional tests. Finally, in vivo isotopic and thermometric methods also give interesting information on acute or chronic anti-inflammatory properties of drugs.