Final answer:
Patients with multiple myeloma have defects in humoral immunity but not in cellular immunity.
Step-by-step explanation:
Patients with multiple myeloma (MM) have defects in humoral immunity but not in cellular immunity. Multiple myeloma is a cancer of antibody-secreting cells, and in this condition, patients produce abnormal antibodies known as monoclonal proteins. These abnormal antibodies affect the humoral immunity, which involves the production of antibodies by B cells, but do not affect cellular immunity, which is carried out by T cells.