Correlation of serum interferon with some clinical and humoral signs of systemic lupus erythematosus.

The serum level of total interferon (IFN) was measured in 15 male patients with systemic lupus erythematosus (SLE) in the active phase and in remission, before and during corticotherapy. The values found were correlated with the clinical and humoral signs of disease. The IFN titer was high in the active phase of disease and was correlated with fever, extension of skin rash, polyarthritis, myositis, autoimmune hemolysis, cardiac and cerebral involvement as well as with ESR, reacting protein C, CIC, ANF and the percentage of LE cells.

S-phase detailed analysis in KB cells by bromdeoxyuridine labelling.

A method based on the sequential BrdU incorporation followed by differential spiralization of the chromosomes was used for analysis of S-phase in KB cells when Brdu was added to the cultures for 19, 24 and 26 hours before fixation. The S-phase was subdivided into three subphases, each recognisable by a specific incorporation pattern at metaphase: late-S (LS), middle-S (MS) and early -S (ES). Two other intermediary subphases, mid-early S (mES) and mid-late S (mLS) have also been distinguished but their accurate identification is generally difficult.

The effect of human alpha leukocyte interferon (IFN) on the frequency of sister chromatid exchanges (SCE) in the KB cell line.

Concentrations of 50, 500 and 5,000 iu/ml of natural human alpha leukocyte interferon (IFN) were added into the culture medium of KB cells, 4 h after serial passage, in the presence of 5-bromo-desoxyuridine (Brdu) at 10 micrograms/ml. Similar cultures without IFN were set up as controls. After 72 h of incubation, the harlequin technique (differential staining of sister chromatids) was applied in order to discriminate among the metaphases of different generations and to appreciate the frequency of sister chromatid exchanges (SCE) in the second generation cells.

Diagnostic value of serum interferon level in systemic lupus erythematosus.

In all the patients with systemic lupus erythematosus (SLE) tested in the active phase of the disease the serum interferon (IFN) level increases above the normal value (20 I.U./ml) reaching in some cases 80-160 I.

Interferon level in human normal sera.

Interferon (IFN) level in the sera of normal humans was determined by their protective effect on a KB cell culture against the cytopathic effect (CPE) induced by vesicular stomatitis virus. The technique revealed all the three known types of IFN. In the investigated population 15 of 37 sera (40%) were found to protect against the CPE at 1/10 dilution, 11 of 37 (30%) still protect at 1/20 dilution, and 7 of 37 sera (19%) still protect at a dilution of 1/40.