The Histamine Story
This amino acid is the direct chemical precursor converted into histamine by the enzyme histidine decarboxylase
Histidine
This generic, non-specific acute response is a "first-line" defense that lacks immunologic memory
Innate Immune Response
Use this four-letter mnemonic to recall the four distinct types of hypersensitivity responses
Allergic
Cytotoxic
Immune Complex
Delayed (T-cell mediated)
Most H1 antihistamines are technically classified as these because they stabilize receptors in their inactive state
inverse agonists
This is considered the pathognomonic hallmark symptom of an ocular allergy
itch
This specific receptor type predominantly mediates immediate hypersensitivity reactions, leading to vascular permeability and smooth muscle contraction.
H1 receptor
Unlike the innate system, this acquired response features specificity and memory, meaning subsequent responses are amplified.
Adaptive Immune Response
This specific immunoglobulin is the primary mediator of Type I "Immediate" hypersensitivity reactions
IgE
First-generation antihistamines cause dry mouth and blurred vision by non-specifically binding to these receptors
muscarinic receptors
Unlike viral infections that produce follicles, ocular allergies are known to produce these on the conjunctiva
papillae
These are the two primary routes for the inactivation of histamine in the tissues
HMT and DAO
These cells stimulate T-cells to mature into Helper T's, which then cause B-cells to transform into plasma cells.
Dendritic cells (or APCs)
This type of hypersensitivity is uniquely T-cell based, antibody-independent, and takes 48–96 hours to develop.
Type IV
Second and third-generation antihistamines produce fewer CNS effects because they stay largely outside of this
blood-brain barrier
This is the immediate drug of choice for treating a systemic anaphylactic reaction.
epinephrine
This is the primary receptor type responsible for promoting gastric acid production and certain immune cell activations
H2 receptor
This humoral defense mechanism is activated by microbe surface interaction in the innate system and by antigen-antibody complexes in the adaptive system.
complement cascade
Graves disease and Myasthenia Gravis are examples of this "cytotoxic" hypersensitivity type.
Type II
This class of drugs works by blocking the calcium influx that stimulates mast cell degranulation.
mast cell stabilizers
This is the name of the first FDA-approved non-injectable, intranasal epinephrine spray
Neffy
Histamine-induced vasodilation can lead to hypotension and this compensatory heart rate response.
reflex tachycardia
These specific B-cells are responsible for secreting antibodies rapidly upon re-exposure to a known antigen.
Memory B-cells
Type III hypersensitivity is characterized by the deposition of these into tissues, leading to local inflammation.
immune complexes
This specific mast cell stabilizer is 2500 times more potent than cromolyn and is effective at reducing eosinophil migration.
Lodoxamide
These are the four "cardinal signs" of inflammation that may indicate a need for combination anti-inflammatory therapy
redness, heat, swelling, and pain