Reverse Triple Negative Immune Resistant Breast Cancer

Inclusion Criteria:

* ECOG Performance Status of 0, 1, or 2
* Metastatic or locally advanced, histologically documented TNBC (absence of HER2, ER, and PR expression)
* Radiologic/objective evidence of recurrence or disease progression after immunotherapy(combined with targeted therapy or chemo ) for metastatic breast cancer(MBC)
* Adequate hematologic and end-organ function, laboratory test results, obtained within 14 days prior to initiation of study treatment.
* For women of childbearing potential: agreement to remain abstinent (refrain from heterosexual intercourse) or use contraceptive measures as outlined for each specific treatment arm
* Measurable disease according to Response Evaluation Criteria in Solid Tumors v1.1 (RECIST v1.1)
* have the cognitive ability to understand the protocol and be willing to participate and to be followed up.

Exclusion Criteria:

* Symptomatic, untreated, or actively progressing CNS metastases
* Active or history of autoimmune disease or immune deficiency
* Significant cardiovascular disease
* History of malignancy other than breast cancer within 5 years prior to screening, with the exception of those with a negligible risk of metastasis or death
* Treatment with chemotherapy, radiotherapy,immunotherapy or surgery (outpatient clinic surgery excluded) within 3 weeks prior to initiation of study treatment.
* Pregnancy or breastfeeding, or intention of becoming pregnant during the study
* History of allergies to the drug components of this trial
* History of eosinophilosis or mastocytosis
* Patients who have been using oral steroid hormones for a long time will need to stop for 4 weeks if they have used them occasionally in the past
* For the Mecapegfilgrastim group, patients had previously received PEG-rhG-CSF in combination with immunotherapy.