Objective—To determine whether human CTLA4-Ig
([hu]CTLA4-Ig) inhibits costimulation-dependent lymphocyte
proliferation in vitro, compare the effects of
(hu)CTLA4-Ig with cyclosporine and steroids on CD4+
and CD8+ T-cell lymphocyte proliferation, and determine
whether memory T-cell function remains intact
in the presence of (hu)CTLA4-Ig.
Procedure—Peripheral blood mononuclear cells
(PBMCs) were stimulated with concanavalin A (costimulation-
dependent mitogen) or phorbol 12-myristate
13-acetate and ionomycin (costimulation independent
mitogens) alone or in the presence of
(hu)CTLA4-Ig, cyclosporine, or dexamethasone;
effects of these treatments on lymphocyte proliferation
were assessed by incorporation of thymidine
labeled with tritium or flow cytometry. Antigen-specific
proliferation was determined by stimulating
PBMCs from 2 healthy cats seropositive for
Toxoplasma gondii with soluble Toxoplasma antigen
alone or in the presence of (hu)CTLA4-Ig or
Results—(hu)CTLA4-Ig inhibited costimulationdependent
lymphocyte proliferation in vitro but had
no effect on costimulation-independent lymphocyte
proliferation. Compared with mitogen alone,
(hu)CTLA4-Ig caused a significant decrease in responder
frequency and proliferative capacity of CD4+ T
cells; however, the effect on CD8+ T cells was not significant.
Cyclosporine alone or with dexamethasone
had a significantly greater suppressive effect on
responder frequency and proliferative capacity of
CD4+ and CD8+ T cells, compared with (hu)CTLA4-Ig.
Compared with cyclosporine, (hu)CTLA4-Ig appeared
to have a sparing effect on antigen-specific proliferation
of memory CD4+ and CD8+ T cells.
Conclusions and Clinical Relevance—(hu)CTLA4-Ig
selectively inhibited costimulation-dependent proliferation
of lymphocytes in vitro and had a sparing effect
on antigen-specific proliferation of memory cells. The
specificity of its mechanism of action suggests that
(hu)CTLA4-Ig may prevent allograft rejection but leave
memory responses to previously encountered antigens
intact. (Am J Vet Res 2005;66:483–492)
Objective—To evaluate effects of apheresis on mesenchymal stem cells (MSCs) and compare those MSCs with MSCs obtained from adipose tissue or bone marrow (BM).
Sample Population—Samples obtained from 6 adult horses.
Procedures—Samples of blood from a peripheral vein, adipose tissue, and BM aspirate were obtained from each horse. Samples were processed via apheresis of blood and techniques reported elsewhere for adipose tissue and BM. Cultures were maintained until adherence and subsequently were subjected to differentiation protocols to evaluate adipogenic, osteoblastogenic, and chondrogenic potential.
Results—Apheresis product had a significantly higher mononuclear percentage, higher platelet count, and lower RBC count, compared with values for peripheral blood. No cell adherence to the tissue culture plates was detected for the apheresis product. Adherence was detected for 6 of 6 adipose-derived and 4 of 6 BM-derived samples. Variations in efficiency were detected for differentiation of adipose- and BM-derived cells into adipocytes, chondrocytes, and osteoblasts.
Conclusions and Clinical Relevance—Apheresis was able to concentrate mononuclear cells and reduce RBC contamination. However, the apheresis product was unable to adhere to the tissue culture plates. In matched horses, adipose- and BM-derived MSCs were capable of producing lipids, glycosaminoglycan, and mineral. The BM was vastly superior to adipose tissue as a source of MSCs with osteoblastogenic potential in matched horses. Additional studies will be necessary to optimize apheresis techniques for horses before peripheral blood can be considered a suitable source for multipotential cells for use in cell-based treatments.