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    Systemic lupus erythematosus

    The following model has been proposed for SLE:

    1. Antigen-presenting cells (APCs) take up necrotic cells and their antigens.
    2. In an inflammatory microenvironment auto-antigens are processed by APCs and presented to autoreactive Tcells.
    3. Autoreactive B cells take up autoantigen and arestimulated to proliferate by autoreactive primed T cells.
    4. Plasma cells derived from stimulatedautoreactive T cells secrete auto-antibodies, which cause inflammatory disease.
    1

    Which of the following biological molecules is never tested positive in SLE?