10.1 The timing rule
The effect of immune therapy depends partly on the amount of beta-cell function present at treatment. In stage 1, stage 2, or soon after stage 3 diagnosis, meaningful beta-cell reserve may remain. In long-standing T1D, immune control alone cannot replace missing cell mass.
Timing determines what immune therapy can save
- 1
Stage 1: autoimmunity, normal glucose
- 2
Stage 2: autoimmunity plus dysglycemia
- 3
Early stage 3: some reserve often remains
- 4
Long-standing stage 3: replacement becomes central
This is why “delays diagnosis by years” and “cures established disease” are fundamentally different claims.
10.2 Teplizumab: clinical evidence of disease modification
Teplizumab is an antibody that binds CD3, part of the T-cell receptor signaling complex. It does not simply erase every T cell. A short treatment course changes activation and the balance of T-cell states.
In a randomized study of high-risk relatives with stage 2 T1D, one 14-day course delayed progression to clinical stage 3 disease: the median time to diagnosis shifted from roughly two years in the placebo group to roughly four years in the treated group.
In the PROTECT study of children and adolescents recently diagnosed with stage 3 T1D, two courses preserved more stimulated C-peptide at 78 weeks. Not every secondary clinical outcome improved.
Disease modification
The therapy changes the trajectory—delaying stage 3 or preserving more residual secretion.
Replacement cure
The therapy restores enough missing islet function for durable endogenous control in established disease.
The teplizumab trial demonstrates that progression from stage 2 to stage 3 T1D can be delayed in some participants. It does not establish a stand-alone curative therapy for long-standing disease.
10.3 Why combine immune mechanisms?
The immune network is redundant. B cells present antigen. T cells require co-stimulation. Inflammatory signals reinforce activation. Regulatory cells restrain responses. Blocking one pathway may create temporary benefit while the network adapts.
TrialNet’s RELAY study tests a sequence:
The logic of sequential immune therapy
- 1
Rituximab reduces B cells, weakening antibody production and antigen presentation.
- 2
The immune network begins to rebuild.
- 3
Abatacept reduces the co-stimulation T cells need for full activation.
- 4
Researchers test whether the sequence preserves beta-cell function longer than a single intervention.
More mechanisms can also mean more toxicity. Combination is a testable hypothesis, not automatically a better treatment.
10.4 What is antigen-specific tolerance?
Broad immunosuppression weakens protection against many targets. Antigen-specific tolerance aims to silence only the harmful response against selected beta-cell antigens while preserving ordinary defense against infections and tumors.
Possible platforms deliver beta-cell antigens using peptides, nanoparticles, engineered bacteria, or specialized cells in a context intended to promote:
- deletion of harmful immune cells;
- anergy, a long-lasting unresponsive state;
- regulatory T-cell responses;
- immune learning without inflammation.
10.5 Why tolerance is harder in humans than in a diagram
T1D may involve several antigens. The important targets can differ among people and across disease stages. A therapy may arrive after the immune response has spread from one antigen to others. The correct tolerizing dose and context are not obvious.
Immune biomarkers can show that the treatment engaged its target without proving that enough beta cells were preserved to matter clinically. A large phase 3 setback for Diamyd’s antigen-specific program in 2026 reinforced that conceptual elegance does not guarantee robust human efficacy.
Other programs—such as tolerogenic nanoparticles, engineered bacteria, and peptide approaches—remain at early stages or lack evidence of clinically meaningful benefit.
Concept questionWhy might an antigen-specific therapy work better in stage 1 than after years of stage 3 disease?
Explanation
Earlier disease may involve less immune diversification and more surviving beta-cell mass. Later disease can include broader immune memory while offering few cells left to preserve.
10.6 The combination horizon
The most plausible long-term role for immune therapy may be alongside replacement:
- a short immune reset followed by replacement cells;
- engineered tolerance to protect both native and transplanted beta cells;
- local immune modulation at a retrievable implant site;
- hypoimmune edits plus targeted control of residual autoimmunity.
Review questions
Review the chapter concepts.
- Why does timing determine what immune therapy can accomplish?
- What did the teplizumab trial establish, and what did it not establish?
- Explain the logic of rituximab followed by abatacept.
- How does antigen-specific tolerance differ from global immunosuppression?
- Why can a changed immune biomarker fail to produce clinical benefit?
Use these questions to identify concepts that require additional review.