Table 1.

Trends of main hormones during transition period and their effect on immune functions

Class	Hormone trend1	Altering factors2	Effect on immune system3	References
Glucocorticoids	Cortisol (+) dry-off and calving time	(±±) Stress induced by milk yield higher than 25 kg/d at dry-off, pen movements, re-socialization, environment, weather, diet, parturition	Immune competence (D-): Down-regulation of selectin-L and cluster of differentiation-18 adhesion molecules on PMN4, impairing their chemotaxis and diapedesis; altered cytokines production through impairment of NF-κB5 functions Immune competence (I-): Reduce feed intake favoring lipomobilization. Induce increased expression of PPARα6, which leads to coordinate induction of enzymes involved in plasma transport, intracellular trafficking and metabolism of fatty acids Inflammation (D±): Stimulates haptoglobin release from parenchymal liver cells	Burton et al., 1995; Drackley, 1999; Drackley et al., 2005; Bertulat et al., 2013; Putman et al., 2018
Catecholamines	Epinephrine, norepinephrine, dopamine (+) dry-off and calving time	(±±) Stress induced by pen movements, re-socialization, environment, weather, diet, parturition	Immune competence (D-): Activation of genes encoding for a variety of cytokines through the cAMP-RBP7 activation Immune competence (I-): Provide the primary stimulus for increased mobilization of NEFA8 from adipose tissue	Higuchi et al., 1994; Burton et al., 1995; Drackley, 1999; Padgett and Glaser, 2003; Do Nascimento et al., 2004; Cooke et al., 2012
Steroids	Progesterone High levels during gestation and rapid fall at calving	(Decrease) Deficiency of dietary n-3 fatty acids	Immune competence (D-): Decrease functional capabilities of lymphocytes and PMN4, reduce capacity to face bacterial infections	Roth et al., 1982; Davis, 1998; Drackley et al., 2005; Lamote et al., 2006; Kelley et al., 2007; Sordillo, 2016
	Estrogen (+) late pregnancy	(Increase) Excess of dietary n-6 fatty acids	Immune competence (I-): Decrease feed intake favoring mobilization of body fats
Protein hormones	Insulin (+) late pregnancy; (-) early lactation	(Altered sensitivity) TNF released by leukocytes during systemic inflammations induce insulin resistance	Immune competence (I-): Increased insulin resistance of peripheral tissues reduces glucose uptake in peripheral tissues increasing negative energy balance condition, mobilization of body fats, liver ketogenesis and accumulation of triglycerides	Bell, 1995; Davis, 1998; Kushibiki et al., 2001; Lucy, 2001; Taylor et al., 2004; Kelley et al., 2007; Bradford et al., 2009; Sordillo, 2016
	Growth hormone (GH) (+) early lactation IGF-1 (-) early lactation		Immune competence (I-): Down-regulation of liver GH receptor during NEB9 increase GH and decrease IGF-1 blood concentration, increasing lipolysis and gluconeogenesis	Lucy, 2001
	Leptin Falls in late pregnancy and remain low postpartum		Immune competence (I-): Can influence feed intake and contribute to peripheral insulin resistance in peripartum, increasing NEB9 condition	Esposito et al., 2014

¹Trend of main hormones: (-) indicates hormones that undergoes a reduction and (+) indicates hormones that increase during transition period.

²Main factors altering normal hormonal trends and their effects: (±) indicates an augmented magnitude of transition period trends; (Increase) indicates an upregulation and (Decrease) a down-regulation in the average hormonal production.

³Effect of the hormone on the immune system: (I) and (D) indicate an indirect and direct mode of action respectively; (+) and (-) indicate a positive or negative effect on immune function, respectively.

⁴Polymorphonuclear cells.

⁵Nuclear factor-κB.

⁶Peroxisome proliferation-activated receptor, alpha.

⁷Cyclic adenosine monophosphate response element-binding protein.

⁸Non-esterified fatty acids.

⁹Negative energy balance.