Inclusion Criteria:
1. Diagnosis of probable frontotemporal dementia
2. Male or female age 18 to 86 years
3. If on medications affecting cognition or behaviors (Such as Atypical Antipsychotics, Acetyl Choline Esterase inhibitors), participants must be on stable dosage for at least 4 weeks prior to screening and should remain at a stable dosage during the course of the study. There are no prohibited medications preventing patients from participating in the study.
4. English language speaking
5. Formal education of eight or more years
6. Stable pharmacological treatment of any other chronic conditions for at least 30 days prior to screening
7. A family member or caretaker (study partner) who is expected to be consistently available, administer study drugs of IL-2/abatacept and attend study visits throughout the study. The study partner is also supposed to provide feedback on patient's cognitive and functional status. In the event that the designated study partner is unable to continue participating in the study, the study subject should provide another suitable study partner to ensure the uninterrupted progress of the study.
8. For FTD patients with limited decision-making capacity, the legally authorized representative (LAR) should be present in the decision-making process and trial participation, ensuring they understand the potential risks and benefits, and consent based on the patient's best interest. Extended time for consent will also be considered to ensure comprehension.
Exclusion Criteria:
1. Serious, active bacterial, fungal or viral infection, active or latent tuberculosis
2. History of severe pulmonary dysfunction
3. History of severe cardiac dysfunction defined as left ventricular ejection fraction \<40%; a history of non-controlled cardiac arrhythmias; history of cardiac tamponade; Unstable angina or MI in the last 3 months
4. Hypersensitivity or allergy to IL-2 or abatacept
5. History of bowel ischemia/perforation, or GI bleeding requiring surgery
6. Hospitalization or change of chronic concomitant medication within one month prior to screening.
7. History of hemorrhage or infarct or \> 3 lacunar infarcts, encephalomalacia, aneurysm, vascular malformation, subdural hematoma, space-occupying lesion (e.g. abscess or brain tumor with the exception of small incidental meningiomas) in prior CT or MRI.
8. Clinical or laboratory findings consistent with:
1. Other primary degenerative dementia, (dementia with Lewy bodies, Alzheimer's disease, Huntington's disease, Jacob-Creutzfeld Disease, Down's syndrome, Parkinson's disease, etc.)
2. Seizure disorder
3. History of infectious, metabolic or systemic diseases affecting the central nervous system (syphilis, Lyme disease, other laboratory values, etc.)
9. Clinically significant, advanced, or unstable disease that may interfere with outcome evaluations, such as:
1. Respiratory insufficiency
2. Bradycardia (\<45/min.) or tachycardia (\>100/min.)
3. Poorly managed hypertension (systolic \>180 mm Hg and/or diastolic \>100 mm Hg) or hypotension (systolic \<90 mm Hg and/or diastolic \<60 mm Hg)
4. Uncontrolled diabetes defined by HbA1c \>8%
5. Alanine aminotransferase level (ALT) and aspartate aminotransferase (AST) higher than two times normal
6. Serum creatinine higher than 2 mg/dL
7. Neutrophil count \<1,500/mm3; platelets \<100,000/mm3; hematocrit (HCT) \<30%.
8. INR\>1.4
10. History of cancer within 3 years of screening with the exception of fully excised non-melanoma skin cancers or non-metastatic prostate cancer that has been stable for at least 6 months.
11. History of acute/chronic hepatitis B or C and/or carriers of hepatitis B
12. Disability that may prevent the patient from completing all study requirements (e.g. blindness, deafness, etc.).
13. Suspected or known allergy to any components of the study treatments.
14. Intake of investigational drug within the previous 30 days or five half-lives of the investigational drug, whichever is longer.
15. Any condition, which in the opinion of the investigator makes the patient unsuitable for inclusion.
16. Contraindication to undergoing an LP including, but not limited to: inability to tolerate an appropriately flexed position for the time necessary to perform an LP; INR \>1.4 or other coagulopathy; platelet count of \<100,000/μL; infection at the desired lumbar puncture site; taking anti-coagulant medication within 90 days of screening (Note: low dose aspirin is permitted); suspected non-communicating hydrocephalus or intracranial mass; prior history of spinal mass or trauma.
17. Known to be pregnant or lactating, or positive pregnancy test at screening ; This study allows enrolling women of childbearing potential and the treatments may involve unknown risks to the fetus if pregnancy were to occur during the study. This risk is mitigated by requiring proof the participant is not pregnant prior to start of treatment and requiring highly effective contraception during and, for an appropriate interval, after treatment.
18. Lack of reliable study partner.
