MWS alert: TN Server Used Threads Too Big

We get these alerts on MWS. Can anyone provide what needs to be done or checked on TN server threads to make it under control.

    Name:          TN Server Used Threads Too Big
    Instance name: TN Server Used Threads Too Big Host.HostName.xxxxxx.IntegrationServer.Port.4444.TNServer.Name.TNServer.TNTaskManager.Name.TNTaskManager.
    Description:   TN Server used threads is too big.
    Status:        Rule Violated
    Definition:    ((TNTaskManager/Used Threads by TN Task Manager/Reading_Value) / (TNTaskManager/Max Threads by TN Task Manager/Reading_Value)) >= (0.9)
    Evaluation:     1 interval of  /  compare.greaterThanOrEqual 0.9
    Rule type:     KPI
    SLA:           No

Thanks for any inputs.