Identify a treatment for psoriasis that targets T-cell activation.

Methotrexate is an immunosuppressive agent that effectively targets T-cell activation, making it an appropriate treatment option for moderate to severe psoriasis. The drug functions by inhibiting the proliferation of certain immune cells, particularly lymphocytes, which moderates the inflammatory response that characterizes psoriasis. By reducing T-cell activation, methotrexate helps to decrease the hyper proliferation of keratinocytes and the associated plaques seen in psoriasis.

Topical corticosteroids primarily reduce inflammation and decrease the immune response at the local site of application. While they are commonly used in psoriasis management, their mechanism does not specifically target T-cell activation but rather works to alleviate symptoms through anti-inflammatory actions.

Antihistamines are typically used to relieve itching and allergic reactions rather than addressing the underlying immunological mechanisms of psoriasis. They do not have a direct effect on T-cell activation or the psoriatic process.

Retinoids, while useful in the management of psoriasis, particularly in some cases of pustular psoriasis, primarily work by normalizing keratinocyte differentiation and reducing inflammation rather than specifically targeting the activation of T-cells.