CD40 and colitis: Therefore, to identify the mechanism of MC-LR toxicity in the gut, we demonstrated that a murine CD40 knock-out model attenuates the effects of MC-LR in mice with pre-existing colitis by decreasing the severity of weight loss, allowing a full recovery in bloody stools, preventing the exacerbation of colonic shortening, preventing the exacerbation of colonic ulceration, and preventing the upregulation of the pro-inflammatory and pro-fibrotic cytokines [85].