This study looks at how people with **lymphoma** (a type of cancer affecting the immune system) respond to flu shots. It helps doctors understand how the immune system changes during cancer treatment by checking **antibodies** (proteins that fight infections) and other immune cells. Patients with conditions like **B-NHL** (B-cell non-Hodgkin lymphoma), **CLL** (chronic lymphocytic leukemia), and **MCL** (mantle cell lymphoma) can take part if they haven't had a flu shot or flu this season. They will get a flu shot and be checked at different times over a year (days 7, 28, 90, 180, and 365) to see how their immune system responds.

• The study involves one flu shot and follow-ups for a year.
• Participants must have certain types of lymphoma and not have had the flu shot this season.
• Exclusion includes recent flu infection, severe allergies to vaccine components, or other medical conditions that might interfere.

This study seeks to improve understanding of immune responses in lymphoma patients, potentially guiding future treatments. Participants will help advance this important research.