Downgrading and upgrading type 1 reactions. Do they exist?

Leprosy Mailing List – April 26^th, 2012

Ref.:   Downgrading and upgrading type 1 reactions.  Do they exist?
From: A Bryceson, London, UK

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Dear Salvatore,

I refer to Prof. Kar’s message << Downgrading type 1 reaction? >> [LML April 10th, 2012]

The problem in understanding type 1 reactions lies with the nomenclature, not the immunology.  Cell mediated immunity is the process that, if all goes well, controls the leprosy infection.  More cell mediated immunity (CMI) results in upgrading and increased control; less CMI results in downgrading and decreased control.

I think of a type 1 reaction as a hypersensitivity reaction between antigen and specifically sensitized lymphocytes.  Imagine the patient, or a nerve, to be a test tube containing antigen and lymphocytes.  Add more lymphocytes (as in upgrading) and the reaction, as measured by titrated thymidine incorporation, increases.  Add more antigen (as in downgrading) and the reaction increases.  Thus it is possible to have a type 1 reaction associated with upgrading and a type 1 reaction associated with downgrading.

Clinically, the reactions are indistinguishable.  The history, clinical examination and bacillary index indicate whether the underlying disease is upgrading or downgrading, and thus the prognosis.  If downgrading continues (the patient does not receive anti-leprosy treatment) the infection is uncontrolled and the concentration of antigen in the test tube continues to rise and will eventually suppress the reaction.

We might have a clearer understanding of reactions associated with shift along the borderline tuberculoid (BT) – borderline lepromatous (BL) spectrum if we were to replace the terms upgrading reactions and downgrading reactions with the terms type 1 reaction associated with upgrading, and type 1 reaction associated with downgrading.

With best wishes,

Anthony