Objective      To determine the effect of costimulatory molecules V-set and immunoglobulin domain-containing protein 4 (VSIG4) which is exclusively expressed in the macrophages on the proliferation and activation of T lymphocytes.       Methods      Mouse peritoneal macrophages from 8-week-old VSIG4 knockout (VSIG4

-/-

) mice and healthy wide-type (VSIG4

+/+

) mice (C57BL/6 mice) were collected

and then co-cultured with T cells respectively under the stimulation of CD3 monoclonal antibody. T cells cultured without macrophages but in the stimulation of CD3 monoclonal antibody served as control

and those without macrophages and CD3 monoclonal antibody as the blank control. Purified T cells was evaluated by [

3

H

]

-TdR incorporation assay. Activity of CD69 was tested by FACS. Levels of IL-2 and IFN-γ protein in the supernatants of the co-cultured cells were measured by enzyme-linked immunosorbent assay (ELISA)

and mRNA expression of IL-2 and IFN-γ were detected by RT-PCR.       Results      In the two co-culture groups

the [

3

H

]

-thymidine incorporation

activity of CD69

cell mRNA and protein  levels of IL-2 and IFN-γ were significantly lower than those in the control groups (

P

<

0.05，

P

<

0.01). And these indicators in the VSIG4

+/+

/T group were significantly declined when compared with those of VSIG4

-/-

/T group (

P

<

0.05).        Conclusion      Costimulatory molecule VSIG4 specifically expressed in the macrophage might play a role in the process of inhibiting the proliferation and activation of T lymphocytes co-cultured macrophage.