Immune System Basics – Similarities and Differences Between Dogs and Humans

The basis of dog allergies (whether an allergy to dogs or an allergy in dogs) is the result of the interaction of the human/dog immune system with substances (allergens) that trigger the allergic response.

The immune systems of placental mammals such as humans and dogs exhibit many similarities e.g. they contain white bloods cells, antibodies, chemical mediators etc., although as would be expected, differences between species do occur, such as the relative concentration levels of specific immune cells. For example:

Comparison of Human and Dog White Blood Cells Composition
Type of WBCs	Human (% of WBCs)	Dog (% of WBCs)
Neutrophils	45 – 62 [1]	50 – 67.5 [2]
Lymphocytes	16 – 33 [1]	16.7 – 29.4 [2]
Monocytes	3 – 7 [1]	2.5 – 7.9 [2]
Eosinophils	1 – 3 [1]	1.7 – 4.4 [2]
Basophils	0 – 0.75 [1]	0.06 – 0.75 [3]

Note: Figure are approximate and can vary notably depending on both one’s source of data and variables, such as the analytical method employed, age, diet, gender, medication and race/breed. Data based on or extrapolated from ^[1] Tao Le, Bhushan and Rao 2008, ^[2] and ^[3]

Variations in physiology impact the dynamic interplay between exposure to pathogens/antigens and the development of the animal’s immune system. For example, humans are bipedal (2 feet), walk upright and use their hands as an investigative tool of the world around them, whereas dogs are quadrupedal (4 feet), physically closer to the ground and exhibit less dexterity, having paws instead of hands. Therefore,  a dog spends a great deal of time exploring its environment using their nose and licking or picking up items from the ground with their mouth.

Consequently, a dog, when compared to the lifestyle of ‘modern man’, tends to be exposed to a higher level of bacteria, viruses, parasites and certain antigens on a regular basis. The outcome is that although the immune system ‘building blocks’ of humans and dogs have much commonality, differences result from the way they adapt to their own particular set of circumstances and the pathogens/antigens they encounter. For example, humans are susceptible to AIDS whereas dogs are not, but dogs are susceptible to canine distemper unlike humans.

The following represents a basic overview of the types of immunity related to:

• 1- All animals
• 2- Vertebrates (such as humans and dogs)