Tislelizumab , Cyclophosphamide, Mitoxantrone Liposomes, Chidamide, and Prednisone in the Treatment of R/R AITL

Inclusion Criteria: * Pathological diagnosis of AITL according to WHO classification in 2016, and pathological diagnosis of AITL according to WHO classification in 2016, and at least one evaluable or measurable lesion meeting Lugano2014 criteria: lymph node lesion, detectable lymph node length\>1.5cm; non-lymph node lesion, detectable extra-nodal lesion length\>1.0cm; * Refractory or relapsed after at least one systemic therapy (including chemotherapy, stem cell transplantation)\*; * Age ≥18 years old, male or female, ECOGPS≤3 points; * Life expectancy exceeds 3 months; * Follow-up conditions. Patients understand the characteristics of the disease and voluntarily join the study protocol for treatment and follow-up. * : Relapse: patients achieve complete response (CR) or partial response (PR), disease progression (PD) ≥6 months; refractory: treatment failure (no PR) or PD \<6 months after the last chemotherapy. Exclusion Criteria: Subjects who meet any of the following criteria are not eligible for inclusion in this study: * Patients with abnormal liver and kidney function, specifically serum direct bilirubin, serum indirect bilirubin and/or alanine aminotransferase, aspartate aminotransferase and serum creatinine\>2 times normal values, unless abnormal liver and kidney function is considered to be related to lymphoma; * Bone marrow failure, specifically defined as absolute neutrophil count (ANC)\<1.5\*10\^9/L or platelets \<75\*10\^9/L or Hb\<90g/L, unless changes in hemogram are considered to be associated with lymphoma infiltration of the bone marrow; * The subject's prior history of antineoplastic therapy meets one of the following conditions: (1) prior mitoxantrone or mitoxantrone liposome therapy;(2) prior PD-1 or PD-L1 inhibitor therapy;(3) Angioimmunoblastic T-cell lymphoma previously treated with histone deacetylase inhibitors; * Chronic heart failure with cardiac function class III or IV; or left ventricular ejection fraction \<50%; or patients with the following cardiac diseases within 6 months: acute coronary syndrome; acute heart failure (Class III or IV of cardiac function class); patients with a history of clinically significant QT prolongation (\>450 ms for men,\>470 ms for women), ventricular tachycardia (VT), atrial fibrillation (AF), heart block, symptomatic coronary heart disease requiring medical treatment; * AIDS, syphilis, active B (HBV DNA\>1\*10\^4 copies/ml) and hepatitis C; * Patients with other malignancies that are not effectively controlled; or with other hematological disorders (e.g. hemophilia, myelofibrosis, etc.), the investigator considers that the patient is not suitable for enrollment; * History of autoimmune disease, receiving immunosuppressive therapy before enrollment, immunosuppressive dose\>10 mg/day or oral prednisone for more than 2 weeks; * Clinically uncontrolled active infection (including bacterial, fungal or viral infections), and drug therapy is ineffective; * Patients with uncontrolled hemophagocytic syndrome; * Patients who have received secondary surgery or above within 3 weeks before treatment; * Patients who have participated in clinical trials of other drugs within 30 days before enrollment or are participating in clinical trials of other new drugs; * Pregnant and lactating women and patients of childbearing age who are unwilling to take contraceptive measures; * Known allergies to investigational drug components; * The investigator considers that the enrollment is not suitable.