Spontaneous immunoglobulin-producing capacity of cultures from lupus patients and normal donors following depletion of cells expressing CD19 or CD38

Abstract

Cells spontaneously secreting IgG or IgM (ISC) are present at a high level in the blood of patients with systemic lupus erythematosus (SLE). By use of magnetic-bead techniques, mononuclear cells from such patients and healthy donors were fractionated according to expression of CD19 or CD38 and the cell fractions were then cultured in the absence of added mitogen/antigen for 5/6 days. Supernatant IgG and IgM were determined and, in addition, in the CD38 experiments ISC were enumerated both before and after culture. Much of the immunoglobulin-producing capacity of unfractionated cells (UFC) from both donor groups was recovered in the CD19- fraction, and no immunoglobulin was produced by CD19+ cells suggesting, unexpectedly, that ISC were not expressing CD19. By contrast, CD38 fractionation resulted in nearly all ISC passing to the CD38+ fraction which produced levels of immunoglobulin approaching 50% that of UFC. On culture of CD38- cells there was a build up in the number of IgG and IgM ISC, this being particularly striking in the controls with numbers well in excess of those in UFC. Not all these new ISC became CD38+, but the maturation process was more efficient in the SLE patients. The possibility is discussed that the spontaneous response in the CD38- populations is due to removal of CD38+ natural killer (NK) cells. Removal of ISC that are present preculture is a helpful initial step in studying ISC generation in the disease.

Fig. 5

Generation of CD38⁺ cells on culture of CD38⁻ cells from systemic lupus erythematosus (SLE) and normal donors. CD38⁻ cells were cultured for 6 days (N1) and were then re-fractionated into CD38⁺ (P2) and CD38⁻ (N2) cells. IgG immunoglobulin-secreting cells (ISC) were determined in these fractions (P2, N2) and in the parent population (N1). There were six patients and six controls.

Fig. 1

IgG and IgM production by cells from systemic lupus erythematosus (SLE) and normal donors that had been fractionated according to expression of CD19. Unfractionated (UFC), CD19⁺, CD19⁻ and reconstituted (RCC) cells were cultured for 5 days. Supernatant IgG and IgM were then determined and mean values are shown with s.e.m. There were 12 patients and six controls.

Fig. 2

IgG and IgM production by cells from systemic lupus erythematosus (SLE) and normal donors that had been fractionated according to expression of CD38. Unfractionated (UFC), CD38⁺, CD38⁻ and reconstituted (RCC) cells were cultured for 6 days. There were 12 patients and 12 controls.

Fig. 3

Immunoglobulin-secreting cell (ISC) levels before and after culture of cells from systemic lupus erythematosus (SLE) patients that had been fractionated according to expression of CD38. Unfractionated (UFC), CD38⁺ and CD38⁻ cells were assayed for IgG ISC. There were eight patients and geometric means are shown with the upper limit of s.e.m.

Fig. 4

Immunoglobulin-secreting cell (ISC) levels before and after culture of cells from normal donors that had been fractionated according to expression of CD38. There were eight donors (IgG) and six donors (IgM).

Fig. 6

Effect of brefeldin A on the ELISA spot assay. Peripheral blood mononuclear cells (PBMC) from a normal donor were assayed for IgG and IgM immunoglobulin-secreting cells (ISC) in the absence and presence of increasing concentrations of brefeldin A. Results are given as percentage inhibition in the number of spots.