CCR8 expression identifies CD4 memory T cells enriched for FOXP3+ regulatory and Th2 effector lymphocytes

CD4+ Th2 cells are important regulators of allergic inflammation. CCR8 is thought to play a role in Th2-mediated responses, however, expression of CCR8 in peripheral blood has not been fully characterized. Using a fluorescent form of the ligand selective for CCR8 (F-CCL1), we identified the leukocytes expressing CCR8 in human, monkey, and mouse peripheral blood. CCR8 expression is primarily restricted to a subset of human CD4 memory T lymphocytes (15%). Approximately 40% of CCR8+CD4+ T cells express Th2 cytokines IL-4 or IL-13 while 13% express the Th1 cytokine IFN-gamma. In fact, 50% of all Th2, but only 5% of Th1, cells express CCR8. Upon anti-CD3/anti-CD28 mAb-mediated activation, CCR8+CD4+ T cells secrete 3- to 7-fold higher levels of IL-4, IL-5, IL-9, and IL-13 and 10- to 20-fold lower levels of IFN-gamma or IL-17, compared with CCR8-CD4+ memory T cells. Two-thirds of CCR8+CD4 T cells express cutaneous lymphocyte-associated Ag while the majority lack gut-homing receptors. CCR8+CD4+ cells express CCR7 and CD62L and are present in spleen and lymph nodes of mice. Approximately 25% of CCR8+CD4 T cells express CD25high while 20% of CCR8+CD4+ express the T regulatory cell transcription factor FOXP3 accounting for 60% of all FOXP3-expressing CD4+ T cells. In conclusion, CCR8 marks a diverse subset of CD4 memory T cells enriched for T regulatory and Th2 cells which have the potential for recruitment into sites of allergic inflammation where they could participate in the induction and regulation of the allergic response.

The interleukin-2 fusion protein, DAB389IL-2, inhibits the development of infectious virus in human immunodeficiency virus type 1-infected human peripheral blood mononuclear cells

DAB389IL-2 is a genetically engineered fusion protein that reduces human immunodeficiency virus type 1 (HIV-1) replication in activated, interleukin (IL)-2 receptor (IL-2R)-expressing human peripheral blood mononuclear cells (PBMC). The level of infectious virus released by cultured PBMC after treatment with DAB389IL-2 was measured by a quantitative microculture assay. The inhibition of p24 antigen production was also evaluated in cultures that differed in duration of infection and activation state. Although the activation state of the cell and the time of DAB389IL-2 addition to the cultures influenced its anti-HIV activity, DAB389IL-2 treatment decreased levels of infectious HIV-1 to 0.1%-6.5% of untreated cell levels. DAB389IL-2 also decreased p24 antigen expression to 10%-48% of controls, even when added as late as 8 days after acute infection. Mutational variants of DAB389IL-2 that lack catalytic activity or IL-2R binding are without anti-HIV activity.

Interleukin-4 receptor expression by human B cells: functional analysis with a human interleukin-4 toxin, DAB389IL-4

BACKGROUND

Studies of human IgE-secreting B cells have proven difficult because of the small size of this population. We have used an interleukin-4 (IL-4) fusion toxin to detect functionally IL-4 receptor (IL-4R) expression on B cells involved in IgE synthesis.

METHODS

In diphtheria toxin IL-4 (DAB389IL-4) the receptor-binding domain of diphtheria toxin has been replaced with human IL-4. DAB389IL-4 cytotoxicity depends on IL-4R binding and internalization.

RESULTS

Addition of DAB389IL-4 inhibited IgE synthesis induced by IL-4+ anti-CD40 monoclonal antibody or hydrocortisone. IgE inhibition resulted from DAB389IL-4 B-cell cytotoxicity because DAB389IL-4 inhibited IL-4-independent B-cell proliferation. Thus induction of human IgE synthesis involves IL-4R+ cells. In contrast, terminally differentiated, IgE-producing B cells no longer express functional IL-4R because DAB389IL-4 only modestly inhibited ongoing IgE synthesis by B cells from patients with hyper-IgE states and only minimally affected IL-4-induced IgE synthesis in normal B cells when the toxin was added at day 7. Pokeweed mitogen-induced IgM synthesis was sensitive to early but not to late addition of DAB389IL-4. Thus the loss of functional IL-4R immunoglobulin-secreting B cells is independent of isotype switching.

CONCLUSIONS

IgE-secreting B cells no longer express functional IL-4R. Therapies for allergic disease that target the IL-4R would not affect IgE-secreting B cells but may block the recruitment of B cells into the IgE-secreting pool. For optimal benefits this approach may be combined with therapies that target IL-4R-, IgE-secreting B cells.

Cholestasis and increased biliary excretion of inulin in rats given 1,1-dichloroethylene

Bile flow and biliary excretion of the inert solute [3H]inulin were monitored in unanesthetized, freely moving male rats for 4 h after oral administration of 1,1-dichloroethylene (1,1-DCE) at a dose of 200 mg/kg. Comparisons were made between 4 groups: fed-controls, fed-1,1-DCE treated, fasted-controls, and fasted-1,1-DCE treated. Biliary inulin excretion was assessed at 30-min intervals as total excretion and as bile/plasma ratio. 1,1-DCE treatment was consistently associated with at least a 2-fold increase in both parameters of inulin excretion within 2 h after toxin administration. In contrast, 1,1-DCE treatment was not associated with changes in plasma inulin values at any time or in liver/plasma inulin ratios at 4 h. Bile flow decreased in all groups: gradually by 30% in the fed and fasted controls, by 40% in the fed-1,1-DCE treated group, and markedly by 65% in the fasted-1,1-DCE treated group. Liver damage at 4 h as reflected by elevated plasma activities of liver-derived enzymes was found only in fasted-1,1-DCE treated rats. Thus the cholestatic effect of 1,1-DCE appears related to the development of liver damage whereas other aspects of the hepatic response to 1,1-DCE may enhanced biliary excretion of inulin.