The present invention provides a method of treating a disease or conditions associated with a dysfunction of TREM2 in a human patient, such as Alzheimer's disease, comprising administering to the patient a TREM2 agonist. In another aspect, the invention provides a method of assaying a biological sample taken from a patient having Alzheimer's for biomarkers to determine potential benefit or if the disease has an increased probability of responding to treatment with a TREM2 agonist.